i dont think it's good :(

[stewartschicks]

ok, so my chicken is a colombian black tail, it has been on and off for the last 3 weeks-ish, at first we noticed she wasnt running around as much as her 3 other friends when we had treats for them, she would stand there with her bottom slouched downwards and slightly closing her eyes and looked very drousy (this was mid-day).we also noticed she had a messy bum- we knew this meant there was something wrong. my mum took her to the vets, they said she was underweight and they just gave us some antibiotics to see if it did anything. so for about two weeks she was alot better still not the same as she used to be. then the last few days she has got worse; her feathers have been falling out her bum is very messy and she has diahreah an i was feeding her earlier and she puffed up and pooed and i noticed the skin around her bum was really prominant and it was very red and sore looking. Shes still been eating and stuff but i dont think she will get any better now :/ poor thing i loved her so much she was very osile and friendly now she is subjude an sad looking would anyone have any idea before we take her to the vets again ?