Piperboy
I think what you are saying is that on the EASTbound leg you had an EASTERLY wind and thus a lower groundspeed. Then you climbed, turned WEST, and found you had a WESTERLY wind? Correct?
Is so then that is standard.
Eastlery winds DECREASE with Altitude and become Westerly as you get higher in the Northern Hempisphere (Earth Rotation).
Only Westerlies become stronger with Altitude.