Mussl Kar

After cording my last set after 9 events I mounted a fresh set. A bit slippery the morning of the first event, but that was expected. Afternoon was no better. Yesterday was event 6 and they still feel like an event 8-9 tire. They never delivered the grip that I have felt with all of the other sets that I have run, and my times showed it. I know where I should be with other consistant drivers and this set has put me at a disadvantage. Anybody have experience with this? This set is maybe a month old to me, but they were made almost a year ago according to the stamp on the tire.