Random white film on axolotl gills?

[Lexolotl]

I have a female melanoid and male leucistic in a 55 G tank with plenty of hiding spaces. I just fed them yesterday, and noticed just tonight that my female has a white film on her gills. The male seems to be fine so far. It looks more slime like than it does like cotton.

Is a salt bath in order? Maybe just a fridging?

 

[Lexolotl]

68 degree water temps.
0 ammonia
0 nitrite
20 ish nitrate

I will be doing a water change tomorrow.