Some of the leaves took damage from the 5/18 freeze as well. My sugar maple leaves wilted up in that and never quite looked the same the rest of the season even though they remained green and "straightened" back out. It was a tough year though between that and the rain/high RH. Even my pawpaws are showing some fungal spots and they're fairly disease resistant.
Seems like if a frost happens up there it would have to be toward the end of the month. Some of the GEFS members have a frosty airmass arriving around that time.