What’s wrong with my Rummy Nose Tetra?

[Polarnick]

So I have 8 rummy nose tetras and they’ve been in my 20G long for about a month now. I had to deal with ich but I cured it with heat and have since lowered the temperature back down. 7 of them are still schooling and look healthy but one has a weird green spot on its head and sits alone under the plants and doesn’t move around much. This green spot is confusing me I’ve tried googling it and can’t find anything? I’ve added a picture of the one that isn’t healthy, but the rest look the same aside from the green spot. Anyone know what this could be?

 

[Delapool]

No picture appeared?

Is the green spot like a bruise?

 

[Polarnick]

Sorry thought I linked it let me try again, don’t think it’s a bruise.

 

[Delapool]

I can’t make out much unfortunately - I was thinking could be just where it lost a scale from white spot but sitting by itself is a worry.

I’d suspect either bacterial or fungal secondary infection.

 

[Polarnick]

It still does swim with the others occasionally, and it’s eating so I don’t really know I guess I’ll just leave it