"Possibly a pregnancy gone wrong? It looks infected which means most likely bacterial. If your water parameters are stable and your water is hard (which it should be for mollies) then I suspect it was introduced into the tank by any recent additions."
Seems really unusual for that particular fish to be pregnant which is why it didn't come to mind first. I've never seen any of the males bother at all in the slightest but i guess it doesn't take much and always a possibility. As for recent additions do you mean new additions to the tank which could change bacterial levels in the water such as new toys and plants if so then there has been no new additions to the tank for months.
"First make sure your amm, nitrite, nitrate are good, then make sure your gh,kh and pH are good for the fish you have, like I said mollies like harder water. If you don't know these measurements have your water tested at a local fish store. You should also do a 50% water change just to be safe and then start treating the water with antibacterial, if you can qt the sick fish that would be best, if not then Take out any activated carbon and treat the main tank."
I did a 50% water change not that long ago. Would you suggest that first of all i quarantine the infected fish first of all then say purchase a water testing kit to test the water and then also purchase the antibacterial you mentioned.
"It would also be helpful to know what is in your tank and how long it has been in there respective to the order you added everything?"
Theres a few resin tank decorations like i said nothing new has been added for a long time. No real plants or anything. There are many other mollies in the tank at the moment not displaying any signs of the same type of infection, illnesses or altered behaviours.
Your speedy reply was very much appreciated Thank You
