It looks like lash material to me, and I can't think of what else it could be. Here are two threads about it.
https://www.backyardchickens.com/threads/my-hen-pooped-something-alarming.1595395/#post-27115908
https://www.backyardchickens.com/threads/salpingitis-antibiotic-questions.1574642/
Hopefully, you caught it soon enough. You can find aquamox at chewy, and they can get it to you fast if you choose to use that one. You can also try the Baytril.
https://www.backyardchickens.com/threads/my-hen-pooped-something-alarming.1595395/#post-27115908
https://www.backyardchickens.com/threads/salpingitis-antibiotic-questions.1574642/
Hopefully, you caught it soon enough. You can find aquamox at chewy, and they can get it to you fast if you choose to use that one. You can also try the Baytril.