Lye is what I suggested using. Lye is sodium hydroxide I think. It helps with the smell. Shouldn't hurt the chickens. Add some straw/hay, whatever to help keep things clean and smelling good.Properly kept chickens and a well-maintained coop/run should not smell, except possibly after wet weather that lasts awhile. Lime is not the best to add as it can burn the birds feet if you get the wrong kind. Sweet PDZ or Stall Dry will help keep odors down, as will regular cleaning. Sweet PDZ chemically alters the ammonia from wet manure, it does not mask odor, it eliminates it.
Better quality feed is more completely digested and used by the bird (or for that matter any animal), resulting in a smaller volume of manure with less odor.
Do you let your birds out to range in your yard? Or keep them enclosed in the coop? 100 sq ft is pretty small for 26 adult birds. Letting them range in your yard will spread the manure over your lawn and gardens and there will be less in the coop.
I'd suggest inviting some friends who are willing to tell you the truth, not just what you want to hear, over to see whether they consider your coop to have enough odor to be objectionable. It is pretty easy to become so used to a nuisance that you do not notice it. Someone who is not always subjected to the condition can look at it (smell it) with a fresh point of view.
Sonoran Silkies bring up a good point about feed. Wasted feed on the ground will likely smell worse than chicken poo. So hanging the feeder at a height they can't waste it will help with the smell and thus your neighbor. I hope all goes well for ya.