hey weedhound - i checked the roots and they look totally fine...also fished around the reservoir a bit and didn't drag out any diseased / dying roots...so i don't think that's the problem...what's really weird is that i was out of my house today for about 8 hours, and when i returned i compulsively checked ec and ph...and guess what?...they're markedly up and down respctively again!

Now, I don't want to get too freaked out as the plants seem perfectly healthy and they only have about twenty or so days to go at most...but is this cause for concern? maybe i'll just drain the reservoir out entirely tomorrow and start afresh.

i should add somewhat abashedly that daytime temps are very hot indeed now (close to 100F), though nights are fine...might that have anything to do with it?
best
jash