Yellow shrunken patches on plums

I would be grateful for any advice please. Yellowish brownish shrunken patches are appearing on some the plums on our victoria plums tree. The patches are appearing on the sunny side. The plums are still green. The tree is 3 years old. There’s a greengage tree next to it and the fruits on that are fine. Last week I put gauze bags on most of the fruits on both trees (to deter squirrels) so I wonder whether that has caused the problem, although the greengage tree is fine. Please see the 2 pics of yellowy shrunken patches below.



I also put bags on the fruit of a jubilee plum tree and the fruits are looking a bit off on the sunnyside but in a differrent way, not shrunken just going brown. Please see the pic below.
Thank you from Rachel.

 

most likely cause is sunburn.
Quite a few of my raspberries have turned white - which is also down to sunburn.

 

Thank you Pete. That’s good to know.