not layed in months

hello. i have three chickens around 18 months old and two of them havent givin me an egg in months. theyre not sick, have clean poop, and not molting. in the summer i would get maybe two eggs from them. but the shell would be quite thin and broke easy. i feed them laying feed 16% they were on 20% for awhile. these are my first chickens and would like to get more in the spring.
i do let them out into the yard all day. thought maybe they had a secret laying spot but i cant find it. the squirrels are think here and my girls have befriended them. allowing them to eat the feed in the coop, sleep in the hay and even play together. maybe the squirrels eat the eggs? i dont know. but getting only one egg a day from my lead hen leaves me questioning my ability to care for my chickens or at the very least hungry.

answers or suggestions are appreciated.
Thanks,
gumygum62