Ok, I have four Guppies and one of them is acting very strangely. The other 3 are totally fine, my water is checking out great on all tests, and my temperature is normal. However, this one female Guppy is just sitting in one spot in the water and looks funny. It's holding it's mouth open and just staying in one spot and barely moving. It doesn't seem to be trying to get air, it's just sitting near the surface. Any idea what's wrong with my guppy?