I don't know how many you've been in flowering, but usually you add something like Budswell once at the beginning of flowering and no more than that. I don't think I'd give much more in ferts because they probably have two or three weeks before they start to die. Then it's time to harvest. Let them flower as long as you can and they will die naturally, but if you load them with ferts you'll need an extra week or so just giving water to flush the ferts. Otherwise you get chemical loaded bud. If the plants look good, I'd probably just leave them alone. Also, distilled water you buy at the store is usually good to use without having to worry about pH.