Illness/Sickness: (New)Black spot on heart

[Anna5603]

This is my juvenile axolotl i got him around a month ago. he eats bloodworms (dried or frozen) and his tank temperature is 62 degrees. his rocks at the bottom are too big to eat,so I don't think hes impacted. this morning i realized his sides looked a little bigger than usual. He also has this black spot inside of him. this is the first time ive seen it. if anyone knows whats going on please let me know ASAP I love him so much I really hope hes okay

his name is meep

 

[Otterwoman]

I"m not sure exactly what's going on, but I disagree that the rocks are too big to eat. Especially when he grows bigger.