Female Platy

[GouramiGirl87]

I have a female platy who seems to have a bruise? or redness on the front right side of her stomach.
Anybody have any idea what this could be?? My platys are a few years old, so I wouldn't be surprised if its just old age.
She kind of hangs out at top of the water with another platy.
While I have your attention, some of my platys are losing their "roundness" in their bellys and they seem to be kind of flattening out like they are not getting enough food...Any suggestions?
Any help is great! Thank you!!

20 gallon-
1-5 inch goldfish
6 platys
1 pleco

 

[WILDER]

Your tanks overstocked.
Water stats in ammonia, nitrite, nitrate, and ph.

All you should have in the tank is the goldfish.

Are you sure the goldfish is not eating all the food and the other fish don't get a look in.

Do the fish look skinny or bloated.
Any worms prutruding from the anus,.
What does it look like when the fish go to the toilet.
Any fish showing signs of a bent spine.
Do any fish swim on there sides.
Sunken in bellys.

Redness and bruising can be injury, septicemia. Is the bruising and redness beneath the skin.
Sunken in belly can be bacterial, fish tb, internal parasites.