Last night I noticed that one of my glowlight tetra is swimming strangely. It's moving like a 'see-saw' when it's swimming and when it's not swimming it doesn't seem to be able to keep still and it's very shakey.It doesn't 'hover' anymore like my other glowlights.
It's not missing any fins, is eating normally. I checked the water last night and everything is fine. It's red stripe is a bit lighter than usual and maybe it's gills are a little red (but I could just be paranoid!).

It's is in a 15 gal(us) with 2 other glowlight
6 neon tetra
5 black neon
2 albino cory

Does anyone have any ideas??

Thanks

Ok, so my glowlight is still not well, when it's not swimming it can't stop shaking, it's worse than it was yesterday and now one of my neon has a white lump on it's mouth but apart from that it seems ok but is attacking the other neon.

Checked water stats again this morning and everything is ok still.

Can anyone help??