Use a mixed grip and chalk, or you're going to find it pretty difficult. At the end of the day you deadlift to work your hamstrings, glutes and back, which is hard to do effectively if grip is the limiting factor.
Secondly can you explain what your programme is? You tell us how heavy your sets are but not the reps, and not necessarily what you're trying to do. I ask mainly because it's possible you've tired yourself out by the time you get to 65kg, if volume at only-a-little-lower weights is too high.