My poor baby is floating on his side

Hi guys, I'm a long time herpetologist/ichthyologist --- but, I'm still pretty new to amphibians, (also new to the forum). I got some new dart frogs and axolotls last summer, (the axies were still in the embryo stage -- I work for the Carnegie Institute Dept Embryology we were studying their development and we don't euthanize). Everything was going great until yesterday.

Yesterday I noticed one of my two axies was having a hard time staying on the bottom and I was concerned. I am now alarmed because he's floating at the very surface of the water on his side, at times he's upside down.

I have taken him out of his current tank to separate him from my other axie in case of infection. I also cleaned out that tank and disinfected it before putting my other axie back in it. I have lowered the sick axies water temperature in case of digestive impaction. (I have not put him in the fridge). The only notable difference in his environment/life is I went from frozen-thawed blood worms to live ones.

I have taken pictures.
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He has something coming out from his vent/cloaca --- not really sure of the terminology here.... it looks a bit red to be feces --- but I haven't been paying attention to his leavings since I have switched over to live.

Ideas? Treatments?

Thanks much.

It certainly sounds like he may be constipated, but I can't access the pictures from Facebook.

Do you have substrate in the tank? Also, what are your ammonia and nitrite levels?