It's hard to tell, as sometimes it's two-fold -- minor chewing or physical damage becomes infected with opportunistic decay microbes, like a bacterial soft rot, worsening the damage. This doesn't quite look like Choanephora rot, one of the more common fungi responsible, but we can't rule it out. Slugs and snails can be common chewers when low-lying fruits are in contact with the ground or where a planting bed is irrigated often. Cucumber Beetle adults can also chew into fruit, among other plant parts. You could inspect the plants after dark to see if slugs or other night-feeding culprits are present.

Miri