First, let me introduce myself. I'm Bart and new to this forum.
I have had 3 society finches for a while (all bought from the same pet shop), 2 females and 1 male. They are all 'a tad different'... the male has only 1 eye, for example, although he doesn't seem too sad about it, he is a very cheerful bird.
I bought one of the females with very thin feathers leaving her pretty much unable to fly. After a few months of special food her feathers are looking nice and healthy and she is now flying happily throughout the cage. And yes, she is tame! I can pick her up and she will sit happily with me for quite a bit of time.
The other female is a special one for me: She is extremely cheerful and loves communicating with people. She is also hand tame and really enjoys sitting on my finger.
I let the three of them have a nest a few weeks ago, and out of all the eggs, 2 have hatched! The babies are almost 2 weeks old and seem to do great! The society finches are great parents.
Now, concerning the last female. She seems to be pretty sick for the last few weeks, although the last days it got worse.
When she gets out of the nest to eat, drink or take a bath, she sits fluffed up a lot and bends her feathers down a bit, like she is trying to squeeze something out. Of course my immediate thought was that she was egg bound, however after picking her up I couldn't feel anything. To me, she doesn't seem egg bound because as far as I know this also goes paired with sitting on the floor of the cage...
Now I guess she is constipated or something. I don't really now what to do and it seems to be getting worse, although she is still very cheerful and responds a lot to my words.
I have put a vitamin mix in their drinking water (Combex V) and I have diluted a very, very tiny bit of Epsom salts in their bath. It's probably a far too small amount, but I'm afraid to put too much in it.
Does someone know what might be bothering her? I have put a video on YouTube where you can see her behaviour:
http://youtu.be/7qNCycUAjQA
She is the left one, the wet one next to her is the one-eyed male. The yellow stuff in the drinking water isn't something dirty, it's the vitamin mix!
And last but not least, here is a photo of the babies.

Thanks a lot in advance. You would help my finch a lot!
Bart