I'm really confused on age of laying hens. I have 4 hen's that are 26 weeks or so and 2 that are 17 weeks. The older ones have been giving me eggs for a couple weeks. On a typical day I get 2 blue/green and 2 olive however, yesterday I got 3 blue/green and 1 olive. They don't change their egg colors so should I assume I have a new layer at 17 weeks?