I'm so very sorry to hear about Snuffles:hugs
You did everything you could for her. It is hard to let them go, especially when you have been giving one extra attention.
I'm glad you were able to find the Penicillin.
If you are wanting to oral drench her with Corid, here is the dosage for that:
https://www.backyardchickens.com/threads/corid-oral-drench-instructions.1211991/
You also want to make the Corid water available for drinking in addition to the drench.
Yes, you can give both at the same time. Corid is a coccidiostat not an antibiotic.
Others may have a different opinion, expiration are also dependent on a lot of factors, how it was stored, used, etc. If your Corid has been opened, it is probably better to buy new. If it's still sealed...
I do agree with @Eggcessive I would treat her for Coccidiosis. Coccidiosis does not always present with bloody stool - that is just one of the symptoms of a couple of strains that a bird may encounter. There are 9strains. A weakened bird can succumb to an overload easily.
Chickens have a...