White strings in tank and lump on side of axolotl?

[Warrack]

Hi, just recently I noticed that my axolotl hasn't been eating as much, and he has been pooping out white strands. Just today a lump appeared on his backside.


His water temperature is average, and I typically feed him around 2-3 sinking carnivore pellets every day, and earthworms about every week.


I attached pictures of the lump; sorry for bad quality.
Can anyone help, and what can I do to treat it? Thanks