Please help me identify what this could be.

[MeanGull]

Hi,

So the HLLE has been improving over the past few months. Slowly at that, but an improvement nonetheless. However, the big white mark on the cheek is totally new! How new you may ask? Well, it definitely was not there last night. It seems to be on top of the skin, unlike the HLLE. Bacterial infection?
Did anyone ever experience this with their fish?

 

[Big G]

HLLE can create large areas, usually in the face area that look like the skin has just peeled away.

 

[MeanGull]

That's just it though. It doesn't look at all like HLLE. The HLLE pit above his eye is very different when compared to the smudge on the cheek.
Quite puzzling.

 

[MeanGull]

It looks more like a thin layer of mold over his skin. What's even more puzzling, an hour later, the patch seems to be getting smaller. However, earlier when I fed them, I did run my finger gently over his cheek and it made no difference, ie. nothing came off, didn't show any signs of discomfort - just kept eating as usual.

 

[MeanGull]

Now it's almost gone, an hour or so after discovering it.

So....