Sick Fish Please Help

[gummibear]

A couple of weeks ago I noticed one white spot on my angelfish's dorsal fin. I decided to wait and see if it would spread, and it did. There are now 5 or 6 white spots on the same fin. I know what ich is and its larger than that and not raised at all. Also, it does not have an cottony texture. It just appears flat. I already treated for a bacterial infection and they are still there. What could this be? I am really frustrated because I chnage my water regularly and keep the paramaters at ammo 0 nitrite 0 nitrate less than 10...In other words I feel like I am doing everything right and still getting sick fish. All replies are appreciated

 

[Laser]

If you can get a picture of the spot that might help. Otherwise, I usually look through these pictures to see if the spot matches any of them.

Tropical Fish Disease Identification with pictures and cures.