I’ve had these for several years now, looks like some bug was eating on them. I spray imidian in the spring after petal fall, but since I have a mixed orchard the early blooming cherries have to wait for the later blooming Euro plums before they get sprayed. I have seen only 1 Curio strike on the hundreds of fruits I have looked at this year, and I checked the dropping ones and there are no worms present. The cherries dropped a lot of their fruit this year, likely because they over fruited last year and were not thinned enough, hopefully that will mean big cherries.
Other than this it looks like a great year, light on the apples, but everything else has a massive fruit set, thinning is going to be a real chore this year.