Hardly organic using Advanced 3-part + additives, just saying.
That's not necessarily true. Plants will thrive up to 7.5 and 8 isn't that far out of range. You can deal with it and looks as if the plants have been. Looks good overall. I'd worry more about input pH whilst using nutes.
Tbh runoff in soil isn't an accurate pH measurement. The water has it's own pH value and picks up whatever particulates and dissolved solids on the way through. It's not a true representation. Actual soil pH might be different. Most of those soil probes aren't very reliable either.
Most accurate imo is via soil test kit using a soil sample.
Imo, you've just gone a little bit over with the nutes. Looks healthy overall. I personally can't see any symptoms that immediately point to pH lockout. I see too much nitrogen.
@ half nutes why?
Dunno, but you should have a better idea once you get your EC meter.
It could be simple as getting more runoff when you feed.
You've come this far and they look good, honestly, good job.
But best you can do is just chill.
One plain watering won't hurt in the meantime on next watering, if you haven't already.
I'd then carry on @ half strength nutes, exactly as you have been and test the runoff EC once your meter arrives.
Nitrogen is easily leached away for the most part, and is usually the first deficiency to show in a healthy garden.
So, I'd start by getting more runoff when you feed.
Might be simple as that, bit of buildup.
No worries, I'll refrain from commenting for a while, think I've said all I need to for now.
Good luck.