I bet the yolks weren't very dark because the chicken's nutritional needs weren't being met. I bet when they start to lay for you the difference will be amazing! I like to crack my eggs next to a store bought egg. The store bought eggs look almost yellow compared to my chicken's dark almost...
Are they old enough to lay? If they are I would give them a few weeks of good nutrition and calmness before they start laying.
I'm glad the hens found you. Sounds like they really needed a break....