I personally have never had ANY luck with Melafix or Pimafix...
I had a fungal infection in one of my tanks awhile back and the LFS
recommended 'kordon rid ich plus'
IT IS NOT INVERT SAFE though!! So be careful no snails or shrimp are in tank. It is however safe for scaleless fish. But it worked wonderfully for me..
Although I am not positive your issue is fungal, however the treatment works for many issues..
Might be something to keep in mind if you have any more problems in the future..
Best of luck!!