Best way (performance wise) to move multiple objects in certain time

hello everyone a few days ago i had an assignment for job interview and it was a match three game. after you matched 3 or more tiles the upper tiles would fall and i used coroutines to move them into their new positions (each tile had an coroutine) because i thought it was more efficient than moving them in update. the reviewer told me that using coroutines cost alot of performace and allocates garbage, i want to know what is the better way to handle this problem