Mollies bellies have gotten big!

[Oakley19]

I have three mollies two black and one Dalmatian. I have had them for five weeks now and there bellies keep growing. The Dalmatian is getting really large and I getting concerned.
I have a 29 gallon tank with 17 fish. I change the water weekly and the ph is slightly high at a 7.5. Other than that I feed them twice a day.

Any suggestions is greatly appreciated thanks! Attachment 1Attachment 1

[Oakley19]

my Dalmatian Molly