PH
 

My ph is 7.5, I've read phosphorous acid is used to lower, most common methods, and materials, are not available here, I could probably get the acid though, ideas...

Best is to actually get closest to the wanted PH by composing your nutrients. I have adopted my nutrients in such way that I almost hit the exact target PH. But that's not evident if you don't mix or manufacture your own nutrients. In case it's still of interest, mono ammonium phosphate is a key ingredient.

Anyway, check your PH again when the ready nutrient has settled for 24 h. If your PH has much lowered by the add of nutrients, and you have no way to get PH-down otherwise, you might consider running a higher concentration. Let's say you actually wanted to have a concentration of 1.4 EC but will push to 1.6 to lower your PH by 0.2 for example. Of course you only compromise by some degree, you can't push nutrient concentration that much (especially with seedlings that should grow under 1.0 EC in most cases). But except for seedlings, it's better to have a adequate PH and a slightly to high (or to low) nutrient concentration, than the other way round.

An alternative to Phosphoric acid is nitric acid (be aware of the nitrate content you add). If you deal with minor adjustments, citric acid (powder or granular form) may be useful to lower PH somewhat. Unfortunately it degrades rapidly.

If you have lemon juice that should work fine, but constantly check as the juce is not stabilized and can fluctuate quick.