What is wrong with my ferret?

My ferret has no energy what so ever...when I take her out to play she just slumps around, much unlike her old self that would bounce, hop around, and lick you whenever she was taken out. A lot of the time I go in my room to find her in her hammock with her eyes open and her head laying over the side just staring. We have a lot of dogs and when summer starts they get loaded with fleas and then Sage (my ferret) got them too. I was giving her baths in Dawn Dish soap all the time and now they are gone but she still has that lack of energy that I thought was being caused by the fleas. Her gums are a healthy color, I always make sure she has food and water in her bowl, and she gets to come out and play at least once a day. She was skinny to begin with, but she looks much skinnier now and just so sad all the time. I love my pets so much and hate to see her so down. Does anyone have any clue as to whats bugging her? Is she sick? Depressed? Is there something I'm not doing for her that I should be? Any thing would be helpful! Thanks so much for your time...