4 month old pullet sick [Hard to breathe, lethargic,runny poos]

[5Chickens]

Hi there I have a 4 month old pullet who yesterday didnt come out of the coop in the morning I found her sleeping in one corner. She was acting a bit lethargic so I took her inside gave her some antibiotics and used vetRx around her nose and under her wings. She seemed to get much better as she was drinking and eating. Her poops were runny. Clear with white and sometimes clear with bits of green. This morning I looked at her and she seems to have gotten worse. She is in one corner lying down completley and when I pick her up she tends to just lie on her side with her head cocked. She doesn't seem to be interested in food. Her breathing has gotten worse. It sounds like a crackle when she breathes in and out. And she seems to be breathing much harder. I was thinking it was a cold because we have had rain and cold weather all of a sudden from high 60s weather.
Thank you