So my acrylic kilt has shrunk... Well... Perhaps that's not how it really happened but....

I have a 5 yard purchased new from a hire shop. It fit fairly well for an OTR garment until my middle spread a bit. I can still use the central holes but the under apron seems to can't a bit and "peek" below the outer apron. Is this likely a result of me weight gain or...?

For reference, it's tagged at 36. I currently measure 40 (upper end of the "adjustability" I would expect). Apron measures 18