Could be a number of things, but it's most likely axle wrap. The taller blocks help to make the wrap worse as you've now given the axle a lever on which to attempt to flex the leaf pack against its will. There are ways to prevent the wrap...add-a-leaf, RAS, Helwig helpers.
Like it said...not the end all be all cure to your problem, but likely what you're feeling.
'13 Platinum - Sterling Gray - 4wd - EB - 3.31 ELD - 7200lb GVWR
F150lifts.com BOSS. RAS. BDukes55 Embroidered. Rigid DOT Dually fogs - SRM backups. CBIs in OEM HIDs.
Kicker Substage. 35% fronts. Bedrug. Bakflip F1 w/ custom bike mounts. EZ Down.