four things affect most deck cutting performance beyond sharp blades... OEM blades, deck leveling, ground speed and grass height.
Aftermarket blades are not sometimes the exact length needed to avoid leaving an uncut area/line in the middle. Deck leveling sets the correct "pitch" for optimum blade performance (see your manual). When the grass is thick, wet and heavy - as it is now - slow down. give the deck a chance to stay clean underneath. When cutting grass, take 1/3 the grass height per cut ( grass 3" high, cut 1" off) if you let your lawn turn into a jungle and then expect your machine to immediately turn it back into a golf course, plan on spend some serious bucks for the pro machines. Good luck.