Your light is ok if those temps are right. I see the big rockwool cubes ,is this ebb and flow or flood and drain ? if so the 24/7 is tooooo much. your rockwool is staying too wet. soil can be a buffer but at the first sign of problems with hydro flush with clean water to stop it quick. When soil starts to go bad it all over. That's the be ? now is water. Where are you getting water because boiling doesn't help. You should use only RO (reverse osmosis) or distilled water. If you don't have a PPM meter you need one. Water over 200 PPM's is hard water and should not be used unless your nutes are for hard water. You can leave it out to let chlorine evaperate if your PPM's are good.Youy will get much more help here try not to get confused. When in dought flush with clean water.