My understanding is that stress can cause symptoms to come on quickly.
If her poop is clearing up and it looks a lot better by Wednesday when you finish the meds, I would consider getting her on vitamin therapy right away.
You can start her on Vitamin E (400IU) daily now, this can help...
Have you taken a sample of poop to your vet for testing to make sure that it is Coccidiosis you're dealing with?
I know it seems a lot of folks are having issues this year for some reason, not sure what's going on.
Photos of the poop?
Very possible that Marek's is a contributor of them...