So after some adjustment with moving light distance, changing feeding pH levels and concentrations, turns out the lights are as stated by the manufacture with the exception of 100% intensity which is actually a little lower....had what I thought was light stress, but turns out these are very very nutrient hungry for autos which caught me by surprise. Increased the nutrient solution concentration and also made some larger than usual pH reductions (dropped to the usual level with suphuric and then bumped further down with citric to get a wider pH swing) and that quickly solved that problem. Less than 24 hours later and they look as good as new again.
The run off pH and grow media is still approximately 6.5 but there for sure will be hot spots of around 5.8-6.2 to give the plants all that they need nutrition wise. Run off and grow media EC is down in the 800ppm range which is somewhat lower than perfect but it's stable and that's the main thing.
Light intensity has been increased to 50% now (still 2 under a single) and the DLI should now be approximately 18-20 for the current height above the plants and 20 hour lighting schedule. I am considering turning the second light on next as opposed to increasing this single lights intensity to 75% as I feel this will give a better spread of light over the whole tent and will give each plant more total light as opposed to have a single point of high intensity light.
Considering if I want to supplement with co2 but I think that would be best kept for another experiment once I know both lights are similar in intensity and give enough total light to warrant a co2 addition when the lighting demands are highest later in the plants life
@Herikus, thanks! Can't wait to get them rolled up. Tall plant looks real frosty, it's a shame it's not gonna go full length but should still be mighty fine.
@Psilocubensis, sulphuric acid is used simply to lower the pH of the nutrient solution, the tap water here is 8.4pH so after mixing usually it's above 7pH before regulation with sulphuric acid.
The citric acid is used to lower the pH further so a pH range is covered over a few hours as the pH naturally rises from the break down and plant uptake of the citric acid. But citric acid has another benefit, if you look up the Krebs Cycle you will find it's actually called the citric acid cycle too, and it's all to do with cell energy production and electron carrying etc throughout the plant. I wouldn't grow a plant without it