Molly Fish Lump/Bump

One of our Mollies has developed a lump on the side (photo attached). We have no idea what it is or what to do. We have separated her from the rest of the aquarium and population. Here is what led up to this:

-She had two pregnancies in the last 3 months -We had a snail problem which we have eradicated and corrected during the last 2 months, removed them and added loaches -Not a single fry (20) has made it past 3 weeks, partially my fault as I was away on business for the first delivery, and the second had only 3 frys. -A guppy, loache, and all of our baby mollies have also past on in the last 2 weeks.

I’ve changed the water, cleaned the gravel, and filters and conditioned everything don’t know what the problem is ?

My last guesses are its a ectopic pregnancy, bacteria, another fish biting her, or a snail that is growing under her scales?

Going to our aquarium over the weekend to get more help too.

Help anyone, serious responses only. Thanks,