Ooh they got worse and now they look like distinctive Ca deficiency!
And we have a winner!
Your whole problem stems from a lack of calcium in the plants' diets. It SHOULD be listed as a macro nute along with NPK, it's so important, lol!! But usually you can get it from tap water or the soil itself, so hydro growers need to supplement.
There is a sticky by Latewood called 'GH 3 part and calmag- all you need'. Find it, read it, memorize it. haha.
You probably won't be able to find it at a place other than a hydro shop. But it's so important that even if you have to mail order it with a rush delivery to save your plants, do it.
The fungicide 3 from walmart is a cheap neem oil treatment, and is great for treating stupid mites. Be careful not to spray too heavily. Mist lightly, let dry, wait a day, mist again. It's good stuff but you can overdo it. Go to a once weekly treatment when you notice the leaves are nice and shiny.