Droopy Leavs? :( Help!

Just copying and pasting this from another forum..guess I put it in the wrong one...:(

Hi everyone. First time poster, second time grower...and were having some issues we never had before...hoping maybe someone can point me in the right direction...

We are flowering indoors in a 3x3 tray with a 600watt light and ballast. For the first week we were flowering there were no issues at all, but about a week ago I noticed the leaves were drooping, turning down, and some of them turned a lighter shade of yellow. Only some of the plants, the others look pretty good. We feared we were over watering them, so the first thing we tried was to cut down watering from 10 minutes 3 times a day, down to 2 times a day for 15 minutes and still look the same.

Maybe Nutrients? Were using the Lucas formula, but didnt add nutes last time because the ppm level kept rising past 700, and keeps going up without more us adding more. Weve also completely flushed our reservoir to make sure it wasnt a nute lock or anything, but here I am...

I will post some pics below and maybe someone might know whats going on here..thanks in advance guys and gals