Weird white bump on molly

[kashea]

So I have a balloon molly in my ten gallon tank and she's about two years old. Lately all my fish have been healthy, but I've just noticed a weird white-ish yellow bump coming out of her and I have no idea what it is. I've attached pictures below- sorry they aren't the best quality- so if anyone knows what it is please tell me what I can do to fix it, assuming it's not perfectly harmless. Thanks a lot!

 

[kashea]

Also, this is completely unrelated but I have another balloon molly in my three gallon tank that seems to be dying of fin rot that keeps coming back. In the past few days he has completely lost his back tail and today he lost the ability to swim upright. I've been trying to make him comfortable and still treating the tank, but I'm guessing there's nothing else I can do? I don't have the means to euthanize him currently and I've never done it before, but I was wondering if others thought it would be best to put him out of his misery, as I imagine he's in a great deal of pain.

 

[Delapool]

I'm wondering if that could be a prolapsed uterus / anus. Would the location fit? Does it change shape? If it comes and goes could be worms but it looked a bit large from what I could see.

For fin rot, water quality is always worth checking. Do you have a liquid based test with readings for ammonia, nitrite and nitrate? Plus ph?