If you are sure you have sharp blades and a properly operating underdeck (Clean & baffles in place), then I agree with Roger.
Cut more often or charge for double cuts.
C & G Lawn Service
2001 GMC Sierra 2500HD 3/4 ton 4X4
Wells Cargo 16ft enclosed trailer
Exmark 60" Lazer Z EPS
Exmark 36" Metro HP
Stihl trimmers & blowers
Ryan Lawnaire V