What would be the reason for lining it from a 5 to 6. Is it a 5w or 6w? What does the rod say the weight is.
Different lines from different companies will do different things. Do you have a problem throwing or loading up the rod with the 5w line? DT lines cast different than WF lines do. There's a lot of variables there.
My questions to you:
What's the weight of your rod. What does it say on it.
What line does it have on it now. WF or DT.
Is the rod to fast for you?
What's your main problem in throwing flies?