binza, i have a hen exactly the same way as your girl. She is older and is past laying. She has done this twice. first time she had diareah as well pretty bad. I am thinking the dia. dehydrated her, thus the comb is not getting held up. She drank a TON of water when coersed into it. She was not eating well at all, fluffed up, same as yours. Not running for treats where she would normally take your hand off. I put her on yogurt, warm mash (water and crumbles mixed) I did not see any evidence of mites, worms, etc. She took aboaut 3 days and seemed to improve and was fine. I really thought i was going to loose her. She looked miserable as well. THis was about a month ago.
She started doing the same thing again two days ago. She seems to be having a hard time breathing as well when at rest. I have started the same routine. extra extra EXTRA liquids for the runny poo and dehydration - comb seems to be perking back up. yogurt, some nutridrench helped as well. Comb is still blue like yours. on the edge. She recently had gotten a lot of peanuts as treats too- wondered if this might have had some cause? dunno.
I have heard that the blue comb is a lack of circulation as well. My roo will have his tips do the blue thing off and on. It used to scare me really bad, but after a year it comes and goes and he is a healthy active boy so i dont worry about it.
i use Ivarmec Ivermectin from Tractor Supply on the back of the girls for the worms and lice/mites as a preventitive. Keep her well hydrated! try some extra nutrition in scrambled eggs, yogurt, nutridrench, mush etc. keep her warm and dry. I put her butt in the sink and washed off the poo and blowed dry afterwards. the warm dryer seemed like heaven to her. THEN I saw she was molting - new feathers coming in all over. any coincidence? Not sure as well.
Keep us posted on your girl and good luck! She looks really healthy as well except for the blue on the comb.
Welcome to the site!