Living soil can self-adjust for normal pH ranges of about 6 (acidic) to 8 (alkaline) for short periods, but it doesn’t do well if you keep applying wacky pH water in either direction. 7.5 might be OK if it never goes much higher, but since it does, that seems a likely culprit. I think Gpaw hit the nail on the head that maybe high pH and low temps are causing a lockout.
That’s one of the reasons I use full peat moss as the base for my soil, oyster meal and gypsum instead of lime, and R/O water. I had big problems with water that was consistently as high as you mentioned. A guy named @RastaRoy starting a dirt company in Michigan advised that high pH water was my problem. He said to mix full peat soil and don’t use lime so the acidic soil would naturally counteract the alkaline water. And it worked. You could add a little 1" layer of peat to the top of your pots, maybe under the straw layer, and see if that helps.
Peat is naturally acidic, and I’d rather go a little in that direction than the other way. Lime is great to buffer soils if you have acidic water, but tough if you have very alkaline water. I got an R/O filter for $150 or something and it’s great neutral water for both drinking and growing.
But this is the internet, so YMMV. 
I hope you get it figured out!