You don't say what breed they are, but at 22 weeks, they're near enough laying age that you can start switching them off to layer feed. The extra calcium in it presents problems in smaller, younger birds, but at their age and weight, it shouldn't present a danger. If you want to stay on the cautious side, buy a bag of each, grower and layer, and mix the half-and-half to start. As some of them start to lay, increase the proportion of layer and provide some oyster shell on the side. (Your feed dealer buys from a distributor -- I suspect if you ask them to, they can get it for you by including it in their order from the distributor.) By the time most or all of your hens are laying, you'll have used up the last of the grower and put them onto straight layer with oyster shell on the side. You'll also have weaned them gradually to the typically lower protein content of the layer feed.
I've got nothing in the world to back me up on this, but I've always been of the mind that introducing the extra calcium of the layer feed as they get close to laying age and weight is good conditioning for a strong layer. They are pullets. They will start laying at some point. A little nudge can't hurt, might help.
My two cents worth.
I just this morning found the first eggs from this years all new flock. Hatched 20 weeks ago yesterday -- I suspect it's a couple of the sex-links that tend to lay earlier than the others who came through. I toss that out not to say that what I recommend above is the right way to do things. More to open the door to say it was some satisfying to start to see results from the effort that's gone into them.
Here's hoping you have the same experience soon. It does feel good.