What is this?

[ToothlessTheAxi]

I started noticing these little red spots on the tale of my axie about 3 weeks ago, I contacted a vet that had experience with axolotls and brought him in to be seen. They didn't find any evidence of a bacterial infection, however, they only did a test using a small sample of his skin. The veterinarian gave him an anti-bacterial injection just in case. It has been a little over a week since the appointment and these red dots are still spreading. They are now all over his body, head, back, tail, belly. They look kind of veiny… I'm still worried. Has anyone seen this before? Could the vet have missed something and should I make another appointment?

 

[ToothlessTheAxi]

Also, he is not showing any weird behaviour. He has not been floating, he eats a lot (earth worms and blood worms, sometimes pellets), his gills are not curled. The only 'weird' thing about him is that sometimes he likes to sit with one of his longs flat along side his body (but he does not always do this). There are no other axolotls or fish in his tank, I have been keeping him in a hospital tank and I do daily water changes and test the water once in a while. So his water is always kept clean. He had a fungal infection in the past but that was treated and has completely gone. Could this be a bacterial infection caused buy the fungus? The vet said he was okay, but it is clearly spreading...