Hi thereCustomer Welcome to JA. I am Buddy, and i will try and help you out. Did you replace same 2 pushrods? Did you adjust the valves after you replaced push rod? Usually what bends push rod is valve to piston contact. Can be valve adjuster set to tight. Can be bent valve or cam follower bad or camshaft itself bad.If you reply back, let me get your engine serial number also.Thanks. Also i dont think missing one oil change would cause this issue.