Help W Angel

[snowboarder99886]

I have a 30 gallon tank with 7 neon tetras 5 platies and 2 angels and one pleco. Noticed one angel not doing well and was sitting in the back. Now i observed that a dark red thing on his lip and in the gills and around one of his fin. He or she is breathing really hard for the last 2 days. Anyone got any help.

Nitrates 20
Nitrites 0
Ph 7
A little amonia but very very minimal less then .5.
Water has been consistantly stable and hes been in there with no problem for about 3 months.