Illness/Sickness: SECOND Axolotl got thin and won't eat! HELP!

Hi everyone! This is my first post, I'll try to include everything you all will need to help me figure this out. Pictures are included, one is just a picture of both of them. Then there are pictures of Skol after he died, of his mouth before fridging, and whatever came out of him while he was in the fridge. Then pictures of Apollo now, looking skinny.

I had 2 axolotls, a mel (Skol) and a lucy (Apollo), but Skol died about a month ago. I just got them in March and they were both doing fine until he wasn't. They both ate regularly and eagerly every other day. I fed them about one bloodworm cube each. On a Monday, Skol ate eagerly and looked healthy; gills weren't turned forward, tail wasn't curved, gills were bushy. On Wednesday, Skol wouldn't eat and his stomach was very thin. I didn't notice that on Tuesday. Thursday we prepared to fridge him and got him in the fridge in distilled water around 48 degrees F. On Thursday before we got him in the fridge, his mouth started to look a bit open. We did a 100% water change on Friday around noon. And by the time I got home from work around 7:40pm, he was dead. His cloacal area looked like it burst and a clear gel-like substance was coming out. My boyfriend said it looked like he had pooped a bloodworm-looking thing while I was at work.

Today I noticed that Apollo's stomach is starting to look like how Skol's looked. Apollo won't eat today, he barely ate 2 days ago. His gills don't look turned forward, his tail isn't curved, and his gills kind of look bushy and healthy. There's no white fluff on him.

The water when Skol died was the same as it is today: (and we just did a 5 gallon water change yesterday)
I have a 40 gallon tank with a chiller and filter.
Ammonia=0
Nitrate ~ 20ppm
Nitrite=0
Hardness ~ very soft
Chlorine=0
Alkalinity=high
pH ~ 8.4 (very high)
Temperature ~ 66 degrees F

PLEASE HELP!
I've tried googling it and reading threads on this site, but I can't figure it out!

THANK YOU!

You could try feeding him nightcrawler worms. Blood worms don't have much protein.

I've tried feeding him canadian crawlers, even cut up, but he won't eat them or tries to and spits them back out.

Sorry for your loss

What colour is the poop? It should be a brown colour, but if it is green it has a bacterial infection.
Try and bump your water hardness up, it wouldn't have caused your issue but it helps healing if it's nice and high.
Do you know how old it is?
Try a few different foods. Pellets, live blackworms, frozen cubes.

He had green poop the day I took him out of the tank and put him in the fridge! Does that really mean he has a bacterial infection? What do I do for that?

Thank you!!!

Here's a link with lots of info on bacterial infections. At the end it's got a good list of safe and unsafe meds. I've heard lots of people use furan-2 so it might be a good starting point. If you have one available near you you can always take it to a vet with axolotl experience. They should be able to test and get more info.
http://www.axolotl.org/health.htm

just adding that a diet of only bloodworms might not be the cause of this but it certainly could have made them more susceptible to infections, if they wont take worms you could try repashy "grub pie" mix, its made of ground bugs and my guys love it (its a pretty messy food as a warning, the poos seem to break apart easier too). i pour it into gummy worm molds and keep it frozen, when room temp its a similar texture to jello and spoils faster

hope you can get him better!
if you want to try raising water hardness i use seachem equilibrium and alkaline buffer, my tap water comes out 0 everything and a 6 pH so i use 1tsp equilibrium and 1/4 tsp alkaline buffer per 5 gal to bring my tank to 12GH and 5KH. you could also order bulk ingredients to make your own mix of salts but i found that the cost wasnt that different and just using these seachem mixes is a lot more simple to me.