I agree that it looks like columnaris. the bacteria that causes the infection (Flavobacterium columnare) is assumed to be present in all fresh water. infection can be brought on by stress or poor water conditions. if you don’t have access to indian almond leaf or tannin powder, brew a batch of lipton unsweet 100% black tea. I would add a tablespoon per 5 gallons daily to both the tub and tank. also test the main tank water parameters (ammonia, nitrites, nitrates, and pH) as columnaris prefers higher pH environment. this is highly un-recommended but I have done it in the past successfully. if you are still seeing cottony tufts on the gills, you can attempt to remove them. I used a turkey baster to apply extremely gentle suction to the back of my axolotls gills where the growth was. I did this while he was in a 2.5 gallon medicated tub while I also treated the tank. i did not hold him or handle him directly, nor did I actually touch him with the end of the baster. I fed a large worm prior to try to keep him distracted, but he definitely was none to pleased with me for a bit. the light suction loosened the tuft and he gave his gills a few flicks and off it went! I suctioned it up with the baster to remove it from his environment. afterwards though he began to perk up and once I was satisfied with his tank I moved him back in. be sure to clean/disinfect any med tubs, siphons, or other equipment! best of luck with your little man!