If you only tightened them 1/4 turn past zero lash, that's not enough. I typically adjust a factory stock setup to 3/4 turn past zero lash.
When you tighten the adjusting nut past zero lash, you're actually "preloading" the lifter a slight amount. By "preloading", I mean that you are moving the plunger inside of the lifter down into its bore by a predetermined amount.
You see, the outer body of the lifter does not directly push on the pushrod in a hydraulic lifter application. Inside the lifter, there is a finely machined bore with a plunger inside of it. The pushrod actually rides on this plunger and not the lifter body itself. The portion of the bore below the plunger, forms a hydraulic chamber where pressurized engine oil (via a metering device inside the lifter body) is constantly pushing up on the plunger to take up valve lash. When the lifter is on the base circle of the cam (valve closed), engine oil pressure forces up on the plunger to take up any lash in the valve train. When the lobe comes around and forces the lifter body upwards, a check valve seals the hydraulic chamber so no oil can escape and the plunger is forced upward (via this hydraulic chamber) along with the lifter body, pushing upwards on the pushrod.
When you are adjusting the valves, you are forcing that plunger down into the lifter by an appropriate amount so that there is room for if to adjust in either direction (longer or shorter), should the need arise. I like to run GM hydraulic lifters at appx. .060" preload. How many turns on the adjusting nut it requires to reach .060" preload is determined by the thread pitch of the stud and the rocker arm ratio.
If you preload a lifter too much, it can hold the valve open when on the base circle. Too little preload and they can be noisy, and if left that way can (and probably will) damage valve train components.
My method for adjusting hydraulic lifters is to do them one at a time. I place the valve that I'm adjusting in the center of it's base circle (ie. the valve directly opposite in the firing order is fully open). I then slowly tighten the adjusting nut to take up the slack while spinning the pushrod with my thumb and forefinger. I tighten the nut until I feel the pushrod tighten up and become difficult (new lifter) or nearly impossible (healthy, pumped up used lifter) to keep spinning with my fingers. This is zero lash! From here, simply turn the adjusting nut or poly lock the predetermined number of turns, lock it down (poly), and go to the next one. This method takes a little bit longer than the factory method, but is much, much more accurate. But once you get the hang of it, it goes very quickly, though.
Back in my Chevrolet dealer days in the early and mid-90's, we did more sets of valve guide seals on the TBI V-6's and V-8's than I can even begin to describe. Believe me, I've adjusted thousands of GM valve trains. The method I described above is definitely the one that I found will set them up properly and prevent any kind of issues down the road.
1995 Camaro Z-28, M6, 396 stroker, Scat forged 3.875" crank, Scat Ultra Q-Lite 6" H-beams, Icon forged pistons (4.030"), splayed 4 bolt w/ARP studs, 12.25:1, AFR 210 heads (2.08"/1.6", 58cc), Comp Ultra Pro Magnum XD 1.7:1 rockers, GM847 cam (234/242 .611"/.632"), Edelbrock LT4 air-gap intake, Spec Stage 3+ clutch, Fidanza aluminum flywheel, 24x conversion, 0411 PCM, TPIS 58mm, Bosch III 42# injectors, Aeromotive 340, Kook's stepped LT's, Kook's custom stainless 3-1/2" merge ORY, Magnaflow