Poorly Hen with yellowish comb

Can anyone help?  Flo (our 2 and a half year old pekin bantam) is very lethargic, and her comb and wattles have a pale yellowish tinge. She is eating but is very listless and shakes her head a lot and sometimes sneezes a few times. Crop does not always seem completely empty the next morning (impacted crop? but she's had the thing with her crop for a while and has always had a healthy appetite so I don't think it's that).

They were wormed with Flubenvet three weeks ago and I have treated the house for red mite and put louse powder on everyone. She did a poo yesterday that looked very slightly greenish and a bit more watery than usual but other poos since then have looked OK.

Does anyone know what it could be? Should I isolate her from the others?

Husband took her to vet on Monday who confirmed comb is pale but not yellowish as I thought. She said she’s showing respiratory problems, infection and possible impaction in crop. Been given course of antibiotics and advised to separate from others and hand feed very runny mash, not hard grain, and give fluids and to keep eye on crop. Unfortunately she has really deteriorated and not eating at all now, producing brown liquid poo and crop feels very full so back to the vet's today but not looking good. Poor little girl.

I hope that you have caught it in time and she makes a recovery.  Keep us posted.

So sorry Flo did not make it.  Hope that you other hens keep healthy.

So sorry