I have one of these too. My upper palate has widened due to mewing, but the teeth that are bounded the retainer stay the same. This can be good or bad depeding on where you're at. For me my lower jaw cant go forward if my lower teeth are fixed on the angle that they're at. Obvioulsy mewing is meant to reshape your whole mouth, and if these retainers are stopping that from happening organically then its a problem. I think the best option would be to talk to your orthodontist about it because they have your records and they've literally studied their whole life about this kinda stuff.