If the first bloke is selling them off and he has 4,000, sounds like he is getting ready for new POL's to come in, so yours would be about 74 weeks old now. They don't lay as much when they get older. We have 64 ex battery chickens and we are getting 36 eggs a day. I'm not thta bothered that we are only getting just over 50% because they have been paying for themselves as we sell the eggs from the front garden.
How much did you pay for them? Older hens are cheaper. If they are happy, they will lay more often as they get more used to you, and they will run to you when they see you. I feel like the pied piper sometimes, I only have to walk outside the back door and they are flying across the run to get to the fence first in case i have something nice for them to eat!!!