sick RIR

[yahoo.com]

Please help! My 1.5 year old Rhode Island has been sick for at least a month. She has runny white poop and drags her bottom around . Her tail feathers are rarely up. All she wants to do is sit on the coop floor. When it first started I brought her in the house and washed her bottom then kept her in for a few days. I gave her Duramycin-10 antibiotic and tried nutri-drench supplement. She seemed somewhat better but she is going downhill now. She still eats and drinks but hasn't laid an egg in over a month. I don't know if I had the dosage right on her antibiotic. Ihave no idea what is wrong!