Hey there - haven't been on and missed all your questions
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Ok, so you don't necessrily need to scrub the litter pans out TOO much, just make sure you're changing the litter out every day and give them a rinse, but no need for intense scubs.
I did it every day for about 3 months to be honest (that's how long it took me to get rid of them), but I would say do it until their medicine is done and the treatments are over.
How often do you have to give them the pancur? I agree with your plan to keep cleaning the wormy one till you see no more worms, the others, when the medication is gone, about a week after, I would go back to normal too.
As far as retraining with the poops go - you can do that now, just as long as you keep up the tray cleaning daily you should be good.
Sounds like you're doing a great job so far. I was so overwhelmed when my guys got it - all that cleaning... but then i fell into a routine.
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Nadia