I am not a big tree frog keeper, but I can try and hit a few points. For breeding, also look at sizes (females=much larger in size than males). Just because one is not croaking could mean it is just not in breeding mode or is not responding to certain stimuli. If you want to breed, try to construct a home made rainchamber.(Instruction can be found by searching the web...they are fairly easy to make as well).
As for feeding, if you think the frogs are starting to get too fat, cut back on feedings and do not offer food as often. If the frogs then look to skinny, the feed more often. There is no "set in stone" guide for feeding frogs. It is normally based on the eye of the keeper.
As for spraying, if the humidity is too low for the frogs to get moisture without going down to the dish, I would spray. When I have kept tree frogs, they normally would not soak in their bowls at all and I would just mist them everyday. It probably is not often in the wild that they go down to the floor to soak in a puddle. So personally, unless you see your frogs soaking often and the humidity is already fine, I would mist.
You might want to post this on the tree frog forum though,as many of those people do only tree frogs or have very extensive experience with them.
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Andy Maddox
Houston Herp Key
The Reptizone