17 month olds hair falling out in clumps?

My daughter was born with a full head of hair. It has always seemed a little brittle and I’m very careful combing it because of this. She was sent home from daycare the other day with a huge clump of hair in a bag and an accident report saying another kid pulled her hair on the playground. When I asked more questions they told me that they saw it happen and the kid barely tugged on her hair at all and said it was something that should be brought up with her pediatrician. Anyone else have something like this happen? We have an appointment with the pediatrician tomorrow, but I’m panicking until then.