Have a Raven 450 monitor on a sprayer and having erratic application rates. Running drop nozzles and fertilizer and has always worked great for many years. Suddenly it went from putting down 30 gal per acre at 9 mph and 40 psi with the full 5 sections activated. Now it won't even make 15 gal at about 15 psi and 5-8 mph with only 3 sections activated, won't generate enough pressure when moving to even have all drop nozzles work. Could this be a flow meter? Or something else?