Use just PHd water from now on until harvest. I've been reading about stressing the plant before harvest so it kicks into high gear for a few days and this makes the nugs bigger and much better. It makes sense to me so I'm trying it. I'm gonna change the lights to 11d/13n and use cold/ice water to trick the plant into thinking that winter is coming for real now so it kicks its system into high bud production mode and they get way bigger within a few days. That's what I would do. Whatever you do, however, you need to do it now because you're almost there, probably less than a week.
