99 Venture Hard Starting

I have just given my van a tune-up about two weeks ago and everything was going hunky-dory until this last week. The wife tells me it is hard starting now. She had stopped to get gas and it took her 8 tries/cranks before it would start. I drove it the other night and it was ok until the same problem got me, it took me 3 tries/cranks to get it started. This van has been very good through out its whole life on starting on the first try, no issues until now.

The tune-up included the plugs (Bosch Iridium, 4 prong) and wires (AC Delco), PCV, serpentine belt, oil & oil filter, air filter and AC freon check (a little low, gave it one can). The only thing I missed was the fuel filter (O'Reilly's didn't have one) and I'll change that this weekend.

The "Check Engine" light is not on, could there still be a trouble code?