Female axolotl has dark spots on lower half of body

Hi! ive been keeping axolotls for about 5 years know and consider myself to be fairly knowledgable about their husbandry. maya, my first axolotl, is a blue gilled leucistic and about 5 years old. today during feeding, i noticed she had these dark spots on her body. im concerned it might be some form of internal bleeding. shes eating fine and is still very active, her gills are pigmented, and shes not showing any external forms of stress. im hoping its just some form of new pigmentation. im going to call the exotic vet first thing in the morning, but if anyone has some information, that would be great. heres a photo of what im talking about.
parameters: ph 7.5 - 8 , nitrates 10ppm , nitrates 0ppm , ammonia 0ppm
substrate: slate tiles
the tank is fully cycled and gets bi monthly 50% water changes, and a full water change every 3-4 months
shes fed mainly nightcrawlers and every now and then she gets some raw shrimp as a treat
thank you for the help!