Okay, if they aren't laying then grower is the best until they begin to lay again - so you're on the right track with that. Rats would likely leave evidence (poop, food dragged into corners), and you should be able to find small holes that they get in and out of.
At night, check your chickens...
Okay, you said they were fed 16% layer in your second comment in this thread so I was under the impression that you had switched them to layer already.
Any chance you have rodents in the coop, as rat disturbance could cause them to avoid the coop at night. There could be something they don't...
If they are not laying yet, you should be feeding them grower. You can switch the whole coop to grower and offer oyster shells on the side for those who need calcium. Layer feed has a lot of calcium in it that can damage the kidneys of birds not laying (and birds don't put weight on as fast)...