Aquariums: Guppy pregnant or indigestion?

Hey everyone!

I am new to the fish hobby and two days ago we bought female guppys from a store. They are now in a quarantine tank.

One of the female looks very round and she also hangs out either at the bottom or just under the surface in a corner a lot.

Is she pregnant, sick or had maybe indigestion issues?

She doesn’t see to have that pregnant dark spot.

Any advice is welcome.