Underwatering? Leaves dont develop and are all yellow..?

Hi i would really need some help to understand whats wrong with my plant.
They are in 7th week of flowering. This is how they looked 2-3 days ago. It is the plant on the right side in the back:

Now the plant look like this:



Is this because of underwatering or what have i done wrong here?

I use a 600w hps, tentsize is 80x80x150, light is about 40cm to planttops, temp always around 25, ph around 6.5, 7 week in flowering and have around 800ppm so not so high..
I have a autopotsystem so they all get water from the same tank.

Thanx for help!

Dude.... Those ladies are burnt to a crisp.. My guess would be that you totally overfed them. Is your meter calibrated?

And the ones that aren't burnt are showing signs of magnesium def..

what strain is that?

Its red cherry berry. Im gonna flush that plant and try to save what i can save there. Didnt think of that i had given that plant to much nutrtions when they drink from the same watertank.

Thanks for the answere!

Have you foliar fed them or sprayed anything on them?

Only sprayed then during veg but no foilar feeding and stopped spraying them when the buds started showing. Well have drained that plant as good as i could. And maybe it will recover some little bit.. And thanx for the noticing of magnesium def, took some epson salt so it will probably be better anytime now. Cheers!

fuckers are FRIED. That is going to be some harsh dog shit smoke. Been there. Sorry bro