Plecostomus growth

Question
I actually have two questions.  We have had a 10 gallon tank with Whisper filter with some Mollies, a Platy, and a Plecostomus for about nine months.  pH, ammonia, nitrite, and nitrate levels are all normal.  We change about 50% of the water at least once every 1-2 weeks, with an 80% change every couple months or when the tank needs it.
Our Plecostomus has recently developed a growth on the side of its mouth, kind of milky white in color and translucent.  It has been present for about three weeks now without much change in color or size.  I was hoping you could give me an idea of whether it is something harmful or not and how to treat it.
My second question has to do with Mollies.  Our female had some babies about 8 months, 6 months, and 4 months ago.  In the beginning, all appeared to be female.  We still have two of the oldest babies left that we did not give away and after 6 months, the fins of one of them have clearly changed into male fins.  Is this normal?  Does it take nearly six months for a Molly's true sex to show?
Thank you in advance for any help you can provide me.  I appreciate it.

Answer
Hi Meredith;

The plecostomus probably just has a cyst. Many animals and even people develop cysts that aren't infectious or harmful. It may even be a wart or something. Plecos can also develop a callous or a blister where they tend to rub on places in the tank where they like to hide. Since it hasn't changed I wouldn't worry about it.

Sometimes baby mollies do take as long as 6 months to show their true sex. Sneaky little devils, aren't they?! ;-)

At Your Service;
Chris Robbins