Repairs 2008 729T6 starting problem 425 hrs

Hello I'm a contractor with many Grasshopper mowers this is my only Gas mower here is the problem just in the last 2 weeks the mower has been hard to start spins very easy acts like there is no fire or fuel but I hear the fuel pump running and I have taken out the spark plugs replaced them and did not really help the problem so I have replaced the in line fuel filter also I have looked at the air filter and the inner filter is black but not wet from fuel. I have been running the mower in 107 degree weather I don't shut the mower off because it acts like a vapor lock. I do not use cheap gas this is the first time since new I have had this type of problem Yes the mower is serviced as the owners manual requests Can anyone give some advice

Just been working on mine. had to clean electrodes in distributor cap... Hope that helps.

this morning I took the plug wire off and found a crack in one of them had to order them so I will install some time next week when new wires show up Thank you for your reply