One other thing I just noticed is you keep mentioning filtered water. Some filters actually add sodium to the water, plants do not like extra sodium.
If this is the case it could explain the yellowing of the leaves, but not the rising ph. I do believe the ph is from the hydroton.
Maybe try using just regular tap water, give it a week and see what happens.

That's just my :twocents:

Best of luck to ya. :hippy: