There aren't really 'other options' especially if you don't know which hen is having the problems.I just called my cat vet but he doesn't do chickens - I have left a message for his colleague who does but isn't in until Tuesday.
Looking for other options.
I still can't figure out who is sick.
Start there. Sometimes it's quicker to start with who it isn't and work backwards.
The food dye around the vent mentioned by @MarkJr often works.