Couple more thoughts about valve adjustment on a running engine...
Stock rockers, be careful you're not rubbing the socket on the rocker. If you do the socket will stabilize the rocker and give a false quiet-point before your half turn extra.
If the rockers are too tight now, you may have a lifter that's bottomed out and not pumping up. So as you loosen, be certain the pushrod is flowing oil. If the pushrod isn't flowing, that's a sign the lifter collapsed and will likely need a few seconds of looseness to pump back up. Never adjust a lifter that's not flowing oil.
If you have poly locks on roller rockers, before doing the half turn of preload, run the lock down snug. Now when doing the half turn, move the lock and the nut in unison, holding both wrenches in the same hand. If you don't do this, the tiny allen head grub screw can't be tightened enough on it's own to hold for thousands of street miles. The head will round out before necessary torque is achieved.
good luck