Agree with Double Haul here. You might try a salt water style hand over hand retrieve when they get like that. It will give you a fast/less jerky retrieve. ( You'd be amazed at the nice fish I've taken with a lefties bug as it gets dragged behind a canoe at 6 knots!.) Play with your retrive untill you get them figured out (for that day!) I would also say that your initial thought to drop a size may have paided off. Sometimes a #10 bug will draw commited strikes that a #6 won't. I'd have changed size before color.
Also, as mentioned, often a half hearted or missed surface strike leaves a fish still wanting to eat. An old trick is to have another rod rigged with a subsurface fly ready to go . ( with line stripped off in a pile/bucket.)If you miss a surface strike. Just drop the rod and throw a subsurface pattern ( Black WB is my favorite) to the same spot FAST. Most times, you'll get that fish as the subsurface fly drops.
BTW, BE gratefull for any action, worked my home pond ( In Tiverton RI) HARD today on a perfect weather day. Just enough wind to cause a ripple, overcast and 48 hrs into a warm front. Fished poppers in all the usuall places. Clousers and WB's in 2-12' of all the good bolder fields and dropoffs. Not one bass and only a few panfish in 4 hours
Fish in that pond have really turned off this week!
Just when you think you got something figured out