Hydro - 3 strains. What consequences after slight veg overfeeding ? Do they look dark ?

It is impossible to discern proper color under grow lights. However, I highly doubt you would be feeding too much unless there is a ratio imbalance in your mix. 1ec is fairly low. Many plants will want more, but this depends on VPD a bit too. This will impact rate of transpiration, which will impact rate of uptake of water in the roots. Higher the vpd, the lower concentration you need to keep the plant happy. If it is drinking slower, you may find you need to up dose if you observe paling and what not... always observe and react, but knowing the cause and effect of this stuff helps choose a path better. (It's the grams of x, y,z nutes per day it needs to maintain rate of growth... the very molecules that make up the cells and their organelles. Just as same DLI over 10 hours vs 13 is virtually the same result, within reason and a photoperiod bloom context.) Hate to contradict someone, but rate of water uptake is more correlated with rate of transpiration. I'd wager when they observed these patterns for their conclusion either RH was high, temps were lower or some combination of those too. -- https://www.researchgate.net/publication/40145027_Effects_of_EC_and_fertigation_strategy_on_water_and_nutrient_uptake_of_tomato_plants This shows the water uptake in the tables by EC. Water uptake actually increased as EC rose from 1 to 2. (ignore the simulated plotted lines, RL measurements only being used here) Leaf area metric had a significant impact on water uptake, which is directly related to rate of transpiration. The conlcusion summarizes some of this and other bits are in the water uptake section. These were tomatoes, but plants are far more similar than ppl want to feel about their favorite hobby :P some exceptions exist, of course. The blotches... is it possible you dripped something on them? Or... is that a light in the canopy? The problem seems to be only in the vicinity of that light. Could be light burns being so close or even heat. Otherwise, leaves look incredibly healthy. Fat fingers. Good color underneath. Veins are proper color, etc. I would never go below 6-ish pH. What ppl say is often more cultural than real. You go below 6 and you have a higher risk of calcium and magnesium issues, which is way more important nutrients than Fe and Manganese, which is the biggest risk you face approaching 6.5 and higher. FWIW, my mix is pH buffed to around 6pH, too, but i believe it is slightly over. Just have the .5reso pH strips. I'm not suggesting 6.5, i'm just saying going lower than 6 is leaving very little room for error on important nutes, and a bit over 6 is perfectly safe with a lot more room for error. The different medium does not change the biology/chemisty occurring in the plant. It's still water with nutes dissolved in it whether standing water with clay balls or absorbed into some physical substrate. Merely a different storage setup for water. Some consistency is key with pH. It looks like you found a well-balanced mix beside those spots. You change pH and you might have to tweak the balance of mix. if you lower it, you may need a bit more Ca than before to mitigate however a lower pH impedes use of Ca... it's not the "uptake" ... roots can't distinguish between dissolved calcium and everything else dissolved in water. Some things may not physically fit, but with hydro nutes that is not a concern. Dont tweak yoour pH unless necessary. It is a hornet's nest of potential domino effects.