How to wash Uniqlo's merino wool sweaters without them shrinking?

Hey guys.

Like the title implies, I am struggling to not shrink my sweaters. I wash it on cold setting, and I air dry it. Usually, this method works for almost all my woolens without shrinkage, even a merino wool cardigan I bought three years ago (also from Uniqlo). I've literally only had this problem with their sweaters, which baffles me because they are made of the same material as the cardigan. Any suggestions?