Looks pretty bad geezer. What medium are the plants in? What's the PH? What's the PPM? What are you feeding them?
Medium is rockwool. Ph is 6.0 PPM running about 650 Feeding them Bontanicare Line.... MagiCal...Pro Tek.... Leaves only on one folding up to show another mg def possibly....
Is it tap or R/O water they're getting? I'm just throwing some questions in so u reveal a little more info. I'm far too noob to actually tell you what ur problem might be. Good luck man, hopefully someone in the know will be by to help soon.
you may need to flush you rock wool it looks like salt build up in soil may its a build up in the rock wool