I have a 36in. Ferris hydro walk behind with a fixed deck. It's got a 14 hp kohler and it pulls me on a sulky (im 240 lbs.). When mowing sometimes it leaves two "stripes" in the same swath i take. Like the right side is lighter than the other side. I thought maybe i had one blade sharper than the other, but its always the same side that is lighter and the same side that is darker. Cant figure it out. sometimes it doesn't do it and sometimes it does. any help is appreciated!