@ Nyajay, several factors can lead to poor hatch rate from natural incubation. This include but not limited to egg fertility, number of eggs set per bird(large birds maximum 12. Small maximum 7 eggs). Time when the eggs are set i.e when the hen starts sitting on the egg( always set the eggs at 6pm so that hatching start 6pm on the 21st day, meaning the hen will have the whole night on the eggs as they hatch). Remember hen will always leave eggs that would otherwise hatch in the nest as long as the 1st chick has jump out side the nest. Ensure therefore that the bird doesn't leave the nest entire day of 21st and half day 22nd. The nest shouldn't be flat. Other factors taken care of ensure the birds are well fed during laying period for quality eggs maintaing ratio of 1 cock for every 5 hen for fertile eggs production. Don't set dirty or cracked eggs. Don't wash eggs with water. Kindly have above as check list and thank me later. All the best.