Why am I getting a noticeable stringer on the discharge side of the mower deck while using doubles? I am running a mulching blade on top and a high lift blade on the bottom. I do not notice the stringer when running singles. I have an Exmark HP 52" deck with a 23 horse kaw. I ran doubles earlier in the year and did not notice this. The only thing I did was replace the deck belt. Ever since then I am having this problem. I have tried going very slow and it does not help. Everything looks good with the deck and the blades are new. Any suggestions?