dying beta

[RVT092481]

I think Betha may be dying. Well I hope she's not but she doesn't look very good.
I came home from work yesterday and went to feed them and I couldn't find her. She came out of one of the hiding things and ate maybe 2 flakes of food (size of pensil eraser) then went back into hiding. She came out a few more times last night but it was only to swim around like crazy and attack the danios (no visible injuries to them that I can see).
Today my husband was looking for her and said that she only came out to swim like a crazy nut then went back into hiding.
She looks really dark now(I posted a picture of her on a previous post to see what she normally looks like). She's looked dark before but only after she'd be sleeping or chilling out for a bit and would wake up. There are no injuries to her or anything on her (ie spots). I got her out of hiding when I got home today and she just swam quickly to the corner and layed on the gravel and didn't move. She kinda curled up a bit as well.
If there's something that I can treat her with that'd be great. I can't really take a picture of her since she's always hiding.
Any help would be greatly appreciated. Thanks.