Hello james12man,
1. I would try and pull back or off as much of those plugs as possible withough't doing too much damage to the roots.
Those become saturated easily and if the stem is continually wet it can cause stem rot. In which case you'd be better off starting over at this stage.
2. 2 inches at the bottom should be OK
3. You defiantly don't need it running all day 24/7. I was concerned that the roots weren't getting enough air if the growing media was saturated/waterlogged. You just need to run the water long enough to wet the growing media, and frequently enough so it doesn't dry out. It didn't look like it would be over saturated because I didn't see algae growing on top. But I also saw your feed line was buried, so it would be possible for the top to be dry (eliminating algae growth) and to be saturated underneath.
I would go with short but frequent watering cycles. Depending on how much water (GPH) each plant is receiving, probably something like 15 min on every hour. Or 30 min on every hour to 1-1/2. As the plants get bigger and temperatures change you may need to continue to adjust your cycles. But the goal is always the same. On long enough to get the growing media wet, and not off so long that the growing media has a chance to dry before the next watering cycle. With tomato's especially it's important to maintain even watering. If the growing media gets soaked and then dries out before watering again the fruit tends to crack. Kind of like filling a water balloon that is being filled slowly, then turning up the faucet all the way at once and the balloon pops.
4. I know you said the drooping didn't seem to be related to the afternoon heat. I wasn't concerned weather the drooping was related to that,
but if it was related to direct sunlight (regardless of the temp). Like if the sun was touching the leaves and it was drooping, then a cloud passed by blocking the sun and it bounced back. Or if it bounced back in the shade of a tree or patio awning etc. etc.. Even in the cool morning or days when it's nice in the mid 70's, if doping occurs as a result of direct sunlight, that's a sign the roots aren't getting enough oxygen.
5. How are you sanitizing the water before you use it?
6 & 7. Temps are fine right now, but as it gets warmer you may need to insulate the buckets to keep them from absorbing heat and keep the root zone temps below 80.
8 & 9. That's good.
10. NEVER completely trust a meter. They can give false readings for many reasons. If there is any question, always double check the results with pH drops. pH drops won't give you false readings. And right now there is reason for questioning the pH. pH is related to
nutrient uptake for plants, and the plants are suffering from nutrient problems. The question is why, and eliminating possible problems is key to finding out.
11. What is "oxidized nutrient filled" water mean?
12. Good, that helps dissolved oxygen levels, helps to keep the
nutrients from settling on the bottom, and helps keep pathogens down.