Red Spot on Axie's Head

[Hixl]

I recently posted here asking a few questions regarding my axie's behavior. The problems were addressed and he seemed to be fine. However, I had to leave for a day on a camping trip. When I came back, he was dead. On his head, there was a large red spot (Blood clot, maybe?) and some red tint to his body, which may have just been his heart/organs. He was only about a month old, if I were to guess.

I tested the water yet again and everything seemed to check out fine. The only thing I could think of was maybe too much stress (a recent heatwave has left the young guy swimming around 73-75, though the heat wave dropped by the time I left) or the new air stone I added since he had been taking an occasional gulp of air. I don't have any pictures, but is there any idea as to what happened? This was my first axolotl and I was really trying to ensure that he was at the right water levels.

 

[SludgeMunkey]

Sometimes they just die. It is the nature of the beast, literally. This is why they lay hundreds of eggs at a pop.

 

[Hixl]

I see, it's certainly reassuring hearing that. Would you be able to guess how long an axie could last a period of stress? He arrived in the mail less than a week ago, meaning that he was in the hot weather for a while. It was probably just natural causes, however I just want to ensure it doesn't happen again. Thank you so much, I'll miss the little guy.