Check the vents on your girls. You're looking specifically for a moist vent (or two, since you have two girls laying). Reproductive malfunctions are pretty common in pullets that are just starting, and a few soft shell, fairy eggs, or deformed shells aren't uncommon, but I'm concerned about the yolky one as that could develop into a much bigger problem down the road, egg yolk peritonitis and down the road, salpingitis. If you can isolate which hens are laying, you can treat those two with antibiotics (one of them needlessly, but the other would absolutely need it to prevent infection now and much worse problems down the road). Would be pretty near impossible to tell which of the two laid the yolker unless she's also wearing it on her rump feathers. I'm sure that many would disagree with antibiotics but I've lost a hen that was simply a beautiful soul because I didn't recognize the warning signs; I'd rather err on the side of caution than lose another to what turned into a lengthy illness and ultimate death.