Most likely nothing to worry about. They're referred to as meat spots or blood spots by some people. Totally common, totally harmless, completely edible. I get them on my eggs frequently. It's basically just a little bit of shed lining from their reproductive tract, sort of like a lady's period. It doesn't really have anywhere to go but into the egg. It doesn't gross me out, I eat 'em, and it doesn't affect the taste of the egg. If it grosses you out, you could cook it and feed it to the adorable kitty that is your avatar. Also, the smaller size of the eggs may be due to summer heat. Most of my girls have been laying smaller eggs these days, too.