[35ppt]

Nothing really jumps out at me. Not familiar with purigen enough to know if it can cause probs.
How long has the tank been running?
Seems like maybe your feeding sched. (once a day) is more frequent than people use ? But considering your parameters, apparently not an issue.

 

[35ppt]

(Probably not the problem, but) have you checked the actual temp of the tank?
I know the wags water (purified) is treated by RO, but is it the same as RO water?