Water stain after fully cured

Hi

Been using epoxy to coat the top of wooden coasters. Tested one out by placing a water bottle containing cold water on for an hour or two. The condensation from the water bottle seems to have left a cloudy ring on the coaster where it’s been sitting. Does anyone have any ideas as to why this might be happening? Maybe I need to leave it to cure for longer but it had been left for 24 hours and seemed to have been cured properly before I placed the water bottle on it.

Thanks in advance x