They both have demodex mange, emily?
What did the vet prescribe? Any questions about the dosage should be brought up with your vet--most vets won't charge for a follow-up phone call. So your first step should be to call the clinic and bring up your concerns.
"We are--each of us--dying; it's how we live in the meantime that makes the difference."
"It's not what you gather, but what you scatter that tells what kind of life you have lived!"
"Be kinder than necessary, for everyone you meet is fighting some kind of battle."