neon tetra with white growth

#1
10gal FW, 4 month old tank, HOB filter
sandy botton
PH 7
nitrite, nitrate minimal
temp 75
chlorine, chloramine 0
25% water change every week

10 neons, 4 RCS, 2 amano shrimp

2 weeks ago i noticed a growth on 1 neon. Figured just an anomoly. Today noticed a smaller growth on a 2nd neon.
here's a pic i found on the net that it looks like
sickfish.jpg
the pic looks like it has a few white dots, not my fish.. my prob is the white growth on the mouth

fish behaves fine, schools, eats well, no change in behavior yet. color is fine
no fish deaths yet. looked around and could not find a great answer as to what this could be.
hoping it is not the beginning of a major outbreak
planning a 50% water change tonight soon as the water warms to tank temp and a 25% change 3 days after that as read in places a water change is 1st thing to do.
 

#3
ty for replying
nitrite and nitrate 0 i should have said
ammonia i havent checked lately as i am going to the store monday to get another master test kit.
I have another smaller tank i will setup as well as I have spare filter i alrdy cycled. I put a 2nd filter into the water I take out after I do a water change I take top 1/2 the water and transfer to another bucket leaving dirty bits behind). Started it 2 months ago this practice as wanted to have a breeding tank for my future shrimp explosion :). thought would be a good idea to have a spare filter setup alrdy. Logic might be off .. but i will continue to read more.
I was thinking fungal infection as well.
I did a 50% water change before writing this. Getting setup to do a 25% change in couple days.
will let ya know what ammonia is at tomorrow night