I know you wrote that they are let out but how large is their enclosure and what is in it for enrichment?But we tend to get a lot of blood streaked eggs. Is there something we can do to prevent this? Is this common in certain breeds?
What exactly are you feeding them, including treats?
Blood streaks on eggs are due to ruptured blood vessels from straining to expel the egg. It can be due to the hen being overweight. Layers should somewhat lean and should have lots of exercise to keep them fit.