Its hard to say, really. But they both need a heater, and one that keeps the water at least at 76'.
She may just not be showing signs of distress as he is.
Sorry, btw- I misread and thought you had not heater >.<" fjsadkflhasdkjfh
But yes, a clean thermometer should be fine to test, or at least a ball park. Its worth buying the fish ones though, theyre like a dollar or two.
Did the fish in that article look like yours? No, right? That is actual velvet.
I think something else is up with him, and that lightness on his head is paleness. Its not fuzzy, right?