I have this problem with button down shirts. I buy one that fits me perfectly and then all of a sudden months later its too small in the sleeves. I wash them very carefully. Only cold water, and air dry. This helps somewhat but the problem seems to re-occur still. I'll try the delicate cycle on the washer, but it's incredibly frustrating.
kazinator|1 month ago
Make sure the shirt is sized so that when you extend your arm laterally, the cuff approaches your knuckle.
If your idea of a fitting shirt happens to be that the cuff just covers a wrist watch when you extend your arm, then you have no spare headroom for shrinkage.