Whats wrong with my plants

Not sure what to do anymore stressing me out in coco fed once a day with green planets medione line 1 third strength 1.5 ml of calmag ro water water her is terrible and salt softened need help scared im going to lose these

Can you change your source water? If your RO system is getting salty when was the last time a membrane change was done?

I fill 2 19 litre jugs at the store once every 2 weeks maybe it's in need of a cleaning at the store lol but not too sure I test the ph only really should I check the ec I guess and ppms I just assumed if I bought it from the dispenser it should be ok I go 1 third strength with medi one part with all the additives and full cal mag than ph am I doing that wrong I feed them 1.5 litres each a night which gives me about 400 ml of run off should I do less water and see what happenes I was just under the impression that you shouldn't let the top of coco dry out and it always is by next watering I could feed less more often but not sure on how much or how often sorry for so much info im just stumped as they were pretty nice a week ago