What are these spots on my Spinach plants
 

well it has been about 2-3 weeks since I started my DWC setup growing lettuce and spinach. Had some issues with High pH but got that resolved and that really helped with the growth. My air stones were floating and migrating to the same place. I fixed them so they would stay sunk and spread them out a bit. What a big difference, my plants loved that. I added a small amount of Hydrogen Peroxide and again I noticed some improvement in growth. But my spinach has spots on the leaves and I am not sure why. My pH is good, my TDS is around 1500 and water temp is staying around 75F. I am using fluorescent lights ( 4 T12 lamps). I was thinking it was a lack of nutrients but not sure. I took some pics hoping this would help determining what is wrong.

I am super new, so take that for what you will, but is 1500 ppm a little high for spinach and certainly lettuce? Could the spots be nitrogen burn? What is the air temp at the grow? Have you grown this crop before? At the same EC?

That TDS is a bit high for your vegetative plants at that size. You might wish to consider dropping it down to around 700 and balancing your calcium/magnesium levels.

My first thought was either too strong or weak nutrient solution. However I don't bother with EC/TDS or PPM meters, so I don't know how that TDS reading relates to the manufactures mixing directions. For plants that small I would be using 1/2 to 3/4 strength nutrients myself. At the same time if you have recently been dealing with a pH problem, the spots you are seeing may just from that. Often times the results of nutrient problems (even from pH problems) wont be seen right away, and take a little of time to become visible (even if it's after the problem was fixed). Because as the plant tissue continue to grow, the damage that was done prior simply become more visible.


However I humidity and air temp can also be factors. Also there shouldn't be any need to balance calcium/magnesium levels. I assume your using manufactured nutrients. Manufactured nutrients are manufactured to be balanced in the first place. In the second place you would need to know what the calcium/magnesium levels were in order to alter them the direction you wanted. EC/TDS/PPM meters cant tell you the levels of individual elements. Altering the balance of your "balanced" manufactured nutrients, would be a trial and error endeavor, and you would only be able to add calcium/magnesium to your solution like with CaMg+ from general hydroponics, or with the individual element salts. But you wont be able to lower the levels of any element in your pre-manufactured nutrients. Unless you were using a 2 or 3 part nutrient, and used less of the part with calcium and/or magnesium in it. Even so, the EC/TDS and PPM meters cant tell you what the actual levels of each element are. Each time you change your nutrient solution, you know your starting with a "balanced" nutrient solution again.

"Manufactured nutrients are manufactured to be balanced in the first place."

Impossible to rely upon with the varying concentrations of calcium and magnesium present in municipal and city tap water. Also, the numbers on the bottle are a minimum guaranteed analysis. It could be higher than that and they don't have to tell you. I learned this the hard way when a batch of GH had way too much magnesium vs calcium in the micronutrient part of the 3-part flora series.

"Impossible to rely upon with the varying concentrations of calcium and magnesium present in municipal and city tap water."

That's very true, but also includes any mineral elements that could be in the water supply. For instance, in my area there would be a lot of extra iron that I know for sure. That's also a water quality issue, not a nutrient balance problem. That's one reason why it's important to use good quality water. Nutrient manufactures can't guess what may be in your water supply in order to be able to adjust for it, and they don't even try. They base their formulas and recommendations for its use on a good quality filtered water like RO water. Or even a pure distilled water, but manufactures don't expect you to buy a bunch of distilled water, so they generally base their nutrients on RO water. It's not their fault if you use something else. Their are company's that will manufacture nutrients based on your specific water supply though.

I don't doubt that there may be times when a manufactures batch of nutrients may not be up to their standards, yet somehow still make it to market. But that's really about their quality control process, and I'm sure would be quite rare. Even so, there are no EC/TDS/PPM meters that will be able to tell you what the individual levels of each mineral element actually is. They can only tell you the total amount of all the mineral elements combined. The only way to know individual mineral levels is to make the nutrients yourself so you know at what ratios you made them, or have them lab tested to find out. And unless you know what the levels of the mineral elements are to begin with, it's just trial and error to try to change them. And again, unless you make your own, you can only raise the levels by adding to them, because you cant take them out of a manufactured nutrient.

hanks for the info about the water etc. I should have started with rain water or bought some purified water to begin with (leson learned). I put a barrel out and collected lots of rain water and will be using that when I need to add water. My letuce seems to be doing really well but my spinach sems to want to flower or something (not sure if spinach does flower), I see some bud like formations and am kinda puzzled. I posted a couple pics since it is so much easier to see what I am talking about.

It appears you have either let it get too warm, or given it too much light. Both things tend to make spinach bolt, where it turns leggy and sets flower.

So should I pull the spinach and start again or just let it keep growing? I mean is it going to be be edible and worth growing?

Edible, yes. Worth growing? It's not very likely to produce any more usable material, it's already bolting. I would suggest starting over, keeping your light to about 13-14 hours daily and keep your temps around 63F.

Alright sounds good, I will grow some more lettuce in the same tote and try spinach in a different setup. My lettuce is really growinnng nicely.

Be careful as lettuce will do the same thing and bolt if you let it get too warm and give it too long of a photoperiod.