Some of my layer is only 14% or 15% and I'm trying to switch to a grower for the hens and roos, for the extra protein. Not easy to find grower here that is unmedicated and I have to drive 50 miles to get flock raiser. I'm not impressed with layer feed. I've read that commercials use 14% because higher protein reduces egg production. Ugh.
Grit -- I'm convinced it should be offered separately and should be granite. I also never buy grit for youngsters as there are always smaller size pieces in the bottom of the bag. Have read on here may times that free range birds don't need grit. I have real doubts about that. Here the "stone" on the ground is limestone which is much too soft to help them grind their food, I believe. If you have a granite stone driveway that they forage in, they probably don't need store bought grit. I feel it depends on locale, your local hard stuff available to them. I don't believe sand is large enough for mature birds to use as grit. I have no real proof, these are just impressions I've formed from reading on here, particularly about crop problems. In 4 years I've never had a problem with a crop. When processing, crops are full of store bought grit.