I agree with the advice given about the PH...keeping it stable is more important.
What concerns me is the frogs. They're eye sight isn't very good and hunt their food by smell, as you found out the cat fish are quicker.
I'd find some way to make sure the little guys are getting food, possibly using a temporary divider and putting their food in a little dish, once you're sure they've eaten, you can remove it. I've also read of people hand feeding them (using long rounded tweezers or a turkey baster).
Good luck
