White slim/powder on fish

[newhobbist]

I've noticed that my Black Molly has a white spots on its body. I'm sure that this is not ICH. These spots are small and not cotton-like so I'm not sure whether it is fungus or not. Additionally, there are larter area (almost whole head) covered in something that looks like white slim or very fine powder.
Today I found that my Rainbow Shark has similar simptoms. Both fish swim at one spot and move only when I feed, though they eat without their usual hunger.
Water parameters are normal with amonia, nitrite at zero and nitrate at 30. I change water every 7-10 days. PH is 6.5, and temperature is 79 degrees.
What can it be and how to fight it?

 

[Devilishturtles]

Is there any new fish or plants? Kinda still sounds like ich to me. Sometimes external parasites will irritate fish, and cause them to overproduce their slime coating in an effort to "shed" off the parasite.

Any chance you can get a picture?

 

[Zagz]

I agree it does sound a lot like ich. If it were a fungus it should be cottony to some extent. I would slowly raise the temp to 86 to be safe. Agreed a pic would be very helpful.

 

[rich311k]

Does it look like salt or sugar sprinkled on the fish? Are they rubbing themselves on tank decorations or rocks?