Black Female Mollie With White Patch Near Eye/nose On One Side

[CarolGoodman]

I have a 27 gallon tank with ideal water readings with one male, 2 females and 5 black mollie  fry. I have had ick and velvet in the past so I know what they look like. I can not take a photo because she is so healthy swimming around hat she wont stay still and you can just see it, dont know if a camera would catch it.
I introduced another fish a few weeks ago, a black mollie with white and glitter like markings to her head but again she looks really healthy. Any idea what is going on?  I have the temp at 80 and leave the lights off most of the time. I also do a water change every 2 days. They are a very tame little crew.
I am tempted o leave alone and just keep an eye out what do you think?
ps it is not like cotton like some say either

 

[eaglesaquarium]

One thing I'd start with is lowering the temp.  There's no need for it to be that high.  Second, what is your gH?  You say 'ideal water stats', but what are those exact stats?
 
 
Personally, I'd remove the molly in question to a QT, and use salt to treat it.  Generally, I wouldn't recommend immediately going to a salt solution, but mollies will be just fine with it, and given your issues with ich and velvet, my guess is that your water is far too soft for the mollies and that's why you are dealing with all these issues.  Mollies really require moderate to high hardness.  The softer the water, the more secondary issues you're going to have to deal with.
 
 
As for the salt solution: start with 1 teaspoon per 5 gallons.... dissolve the salt in a pitcher of water and slowly add the solution to the QT.   Then skip a day.  The next day, add another 1 teaspoon per 5 gallons.  Skip another day.  And the 5th day add another 1 teaspoon.  Then leave well-enough alone.   Mollies are fish that can actually handle a full marine salinity if properly acclimatized to it, though I wouldn't recommend it long-term.  This salinity isn't 'high' or even lose to that, but it is enough that it might at least slow down any infection, parasite, etc. that you are dealing with.  And what it definitely will do is increase the hardness of the water, which is going to help your fish in terms of dealing with water that is too soft.  
 
 
 
 
If you are dealing with soft water (which I believe you are based on the issues you have been dealing with), you can increase the hardness by adding a bit of crushed coral to your tank or filter.  It will help your other fish from developing any new issues as well.