Apple and pear trees, 5 ft. apart with a small fir tree in between — is this the cause of no blossoms on trees?
Due to water starvation?
Fir trees and fruit trees are always a bad mix due to firs causing the acidification of the soil around them. They cast too much shade also and will affect the growth form of surrounding trees adversely as a result. Water competition is also an important factor as you suggest.