New black on my axoltl?

I have a 5 yr old Leucirite male axy. He is healthy & eating bloodworms normally. He has started to develop blk behind his rear legs on his underside and now on the tips of his toes. At first I just thought aging but it seems to be spreading. My research makes me think bacterial, my vet doesn't know axys? Any ideas?

Hi there, does it seem to be fluffy or on top of the skin? or does it seem like it's part of the slime/skin? If it's on top of the skin I would say it might be a bacterial infection. If so, this can be treated with antibiotics and fridging I think but you'd need to do some research on that or contact a reptile and amphibian specialist for more advice - I have no experience with this personally so can't give specific advice.

A few questions, how are the gills looking? How is the slime coat around the body looking? What are the parameters of your tank - ammonia levels, temperature, etc? Is he showing signs of distress? if so, what are they and how severe? Use these questions to rule out things like ammonia burn. Also, if the tank temp is too high it leaves axies more likely to get an infection due to stress in the first place so make sure your temp is at least below 20 degrees C (sorry if that sounds a little patronising). If it's under on in the skin, it could be simple pigmentation changes as the axie gets older, but I wouldn't count on that.

these threads might help you!
Illness/Sickness: - Hi I need help,advice please
Illness/Sickness: - New appearance of black spots

It appears as though some of this black will come off easily so assuming it is bacterial, and will be consulting my vet. He seems healthy otherwise , gills seem normal and water is ok.
Will try to treat bacterial and update. Thanks for all feedback.