Dear Jonathan, You could expect 6-8 inches or more per year once your plants are established. Pyracantha in N. Illinois are likely at the edge of hardiness and best if they are recieving winter protection. Pruning in the Spring to remove any winter damaged growth is best. Pushing new annual growth by high rates of fertilizer will typically result in a lot of winte dieback and potential fireblight disease outbreaks. if you do fertilize, once in the Spring is enough.
Sincerely, Richard Hentschel