She is a little older, with her comb that color and breathing, could have to do with her heart, at least thats what it sounds like instead of something that needs antibiotics.
If they don't have any discharge, i wouldn't worry. They could have gotten some feed,straw, wood chips, whatever you use for bedding, ect, in their nose. Ive had chick's sneeze, as well as my older chickens when i throw feed out and they run right into the midst lol.
If you didn't see any life in the candling method then i would say they weren't viable. 7 to 10 days past due date is quite a while, i wouldn't leave them much longer then your just going to have a bunch of stink bombs. Sorry about your hatch 🥺
If it was your broody hen hatching the eggs it was nothing you did wrong, you just have to let them do their thing. Also, if this was a new hens first time sitting then that could be what the issue was. Sometimes on their first round it just doesn't go as planned. You just never know sometimes...
I bought a couple last year and just now hatched one of her eggs last night. Bred with my Blue Birchen Maran rooster, born with fully feathered feet as well. Can't tell yet what color exactly the chick will be because she is not dry completely yet, but she is a BIG chick lol. Super cute too. I...