2-year old not shedding out

My filly just turned two last month and she hasn’t shed out completely. She has patches of long hair all over her body - looks like a Cushings horse. When I purchased her last year, she wasn’t in the best condition but I’ve had her since April 2021 and she has had a balanced diet, dewormed regularly (and fecal tested). My vet said that it can take a few years for their metabolism to straighten out and the coat to normalize…anyone else have this happen?

My daughters mare was really slow to shed for many years. We feed a RB now and add an all purpose mineral to it and she is shed out just like the others now.