First time poster long time viewer. I have a 1999 high mileage Blazer that I have owned since new. My high school daughter uses this vehicle. Last week, took the truck to fill it up and no issues what so ever. Went to use the truck the next day and would not start. The engine cranks and almost catches but won't start. I followed the fuel pump pressure tech from the Captain and have the following results. Fuel pressure at the outgoing side of the fuel filter is 85 lbs. with the pump running. After 10 minutes the pressure drops to 70 lbs. Fuel pressure at service port is 64 lbs. with pump running and drops to 56 lbs. with no pump running. Pressure drops to 52 lbs. after 5 min and 51 lbs. after 10 min. With everything I have read, my pressures are good and not an issue with fuel delivery. Is this correct? What would make this truck go from a daily driver to a no start condition over night?

Thanks!