Brainstorming/advice needed lovelies

I ordered 2 Itti seconds - they have been washed - one is fine - i put the other one on Z man this morning - and the fit is terrible. They are both Mediums, and I have 4 other mediums that all fit well, but for him to wear it it would have to be only one snap only - it is like a smaller size - a small. Would this be possible? I would have thought that if it was a second due to incorrent tagging by them, that they wouldnt be able to send it if it is really a small etc.

Should I email them or did I just luck out because it is a second???

EDIT - Oh my gosh I just saw my ticker when I posted - Zander is 9 months old today WAAAHHHHHHHHHHHHHHHHH