Alright - first things first: is little Apollo quarantined!?!?! I know that you got your new little frogs at relatively the same time, but you need to be very VERY careful about cross-contamination! Especially since little Apollo is exhibiting some "sick" symptoms!
If I were you, I would (at the very least) separate Aphrodite and Poseidon into a separate quarantine (temp) tank - and let Apollo be in his own tank until you know that he is okay! Ideally, to be honest, I would have each of them in their own separate quarantine tank for thirty days prior to introduction to make sure each is healthy and happy. You don't want one sick froggy introducing that illness to the others. I can't quite tell from your posts if you've done this or not, but I would highly suggest it.
As far as little Apollo: I've never heard of just "warm water" helping a frog that's not eating. How long as he not been eating? How old is he? How big of crickets were you feeding him? When was the last time that you saw feces from little Apollo?
Those are the first questions that come to mind. It's true he could be impacted, but there are also other problems that could be in play, mainly parasites. Frankly, that's the first place I would I check.
In other words, my suggestion is as follows:
1. Quarantine (if you have not already) little Apollo from the rest of your bunch, to insure the lack of cross-contamination in case of bacterial/fungal disease. Make sure that you sterilize to prevent any cross-transfer (i.e. pour boiling water on temporary tank decorations to kill bacteria/fungus etc., and completely sanitize hands prior to spraying with frog-treated water...we use latex gloves that we wash with soap and then spray down, disposing with each handling of a different frog given that one is in quarantine)...What you are doing now is a good quarantine setup - "frog safe" watered down papertowels with a hiding spot/pond.
2. Locate a vet. It's a good bet, given the time that you've had little Apollo (from the posts I'm guessing two weeks?) that you'll need to contact a vet. Again, please clarify how long he has not been eating...Nevertheless, a fecal culture will be a good thing and a good place to start with a new froggy (especially one that is not eating)
I hope that helps!!!