Put some extra holes in the tub. Higher humidity and the right temps will cause bacteria infections if cages aren't cleaned out right.
I have 2 caatinga here that just have not grown either. Mostlikely something is wrong with them and will not make it. You have to remember in the wild these frogs wouldn't survive. In captivity we baby along the weak animals and get them to survive.
You may have done nothing wrong and it was its time to go.
Don't stress too much