Hi. I think I would take her off the oil of oregano for a bit and see what happens. I haven't found any data yet if oil of oregano can build in their system to a toxic level.
I don't think Tylan is going to do anything, it's for respiratory issues. I would do an internal exam for an egg. It's hard to know why they are sick, could she have heat stress? I've had to bring a hen inside a few times so they can recover from the heat. Is she molting?