In my first batch I went with 22% for the first 3 weeks and then 18% from then on out, as recommended by Meyer Hatchery. They claim a lot of the leg and heart issues people see are from feeding too high of protein for too long. I had really good results with that method. Birds dressed out ranging from 6.5 to 8.5 lbs. No leg or heart issues. So I'd go with the 18%.Also, picking up more feed this weekend. Another bag of 22%? or 20% or 18% protein? Brand is Country Companion if it matters.
This is the guide from Meyer I used. It's pretty comprehensive and you can even see if your chickens are on track with their weights, and an estimate of how much they eat from week to week. Hope this helps.