Hey everyone. I'm new to owning chickens so I basically have no idea what I am doing

I have 3 barred rocks that are 6 months old but no one has layed yet. One has a very red comb but she has not started squatting or getting noisy yet (which from everything I've read is normal laying behavior). Is there something I can do to encourage her to lay? I also have 1 silver laced wyandotte (not sure if its a he or a she) that is 5.5 months old. 2 easter eggers that are 5 months old ( not sure if they are boy or girl either) and one rooster that I about to sell because he has started to crow. I have just changed their food from laying pellets to game bird crumbles to increase the amount of protein in their diet hoping that would help them lay. I live near New Orleans, La and although it has been hot, their coop is under a tree and the temperature has only been around the low 90s. Their nesting boxes are milk crates (I have 3 uncles and a cousin that are milk men) turned on their side with pine shavings. I have put a plastic easter egg inside one of the nesting boxes but they have not gone into the nesting boxes EVER. They sleep ontop of the nesting boxes and during the day they hang out underneath the nesting boxes.
I let them out from about 6pm to 8pm Monday -Friday and a lot more on the weekends schedule permitting.
How would I know if they are eating the eggs? I also give them ground up oyster shells with their food.
Thank you for any help.