try picking them everyday see if it changes.
found this
https://starmilling.com/eggs-with-blood-spots-safe-to-eat/
and this
The cause of a blood spot is simply a ruptured blood vessel on the yolk's surface as the egg is forming. This is a natural, benign process for both hen and egg. Instances of blood spots can increase when hens in a flock get excited by changes in lighting, changes in temperature, or simply shifting seasons.
found this
https://starmilling.com/eggs-with-blood-spots-safe-to-eat/
and this
The cause of a blood spot is simply a ruptured blood vessel on the yolk's surface as the egg is forming. This is a natural, benign process for both hen and egg. Instances of blood spots can increase when hens in a flock get excited by changes in lighting, changes in temperature, or simply shifting seasons.