Lawnmower streaking

[bigge31566]

I have a Bunton 72" mower with 3 blades, and it leaves streaks in lawn and even more in heavier grass, I am using Oregon 91-627 straight hi-lift 24 1/2". What could be causing problem

 

[Lawnranger]

Bent blade, worn spindle bearings, warped deck, deck not level, broken deck hanger weld are just a few ideas that come to mind. What have you checked???