I'm thinking it's not a ph issue and I say this because I ph every gallon of liquid my plants see. I now know from experience that the soil ph is going to rise as the grow progresses so I generally ph everything to around 6.3. Almost everything I use is organic and using smart pots and seeing the results time after time of the root system that develops in them, again, I don't think it's a ph issue.
Let me be clear, I don't know what causes the claw but from what I've read it could be a too much nitrogen issue...well they got their first dose of bloom nutes today along with some cal-mag. Let's see what develops in the next couple of weeks with the drop in N.
Edit. Speaking of smart pots, I can't recommend enough for those who use containers to try them and for everyone, rope ratchet hangers for your lights, the ganja god's gift to growers.