I've never grown them, but I saw this advice. Maybe they need to be raised to prevent them from rotting?

"Melons need good, warm, steady summer weather to perform well. You can boost their chances by using row cover for their first month of growth in the field. At the very least, avoid mulching until the soil has warmed up sufficiently. As fruits mature, use shards of ceramic pots or thick, flat, porous stones to elevate them off the ground and reduce the chances of rotting fruit.

Except for watermelons and charentais types, most melons are harvested at the "slip" stage, which means that the fruit detaches easily from the vine when lightly tugged. The harvest window in our area is brief--fresh local melons are available from about the third week of August to the end of September. After that, the cool weather prohibits any immature fruit from ripening fully."