Bill. Upon pulling out the bumpstick and verifying that you have a lobe slowly destroying itself, I'd suggest contacting Isky and see if there are some warranty considerations you can use to your advantage. I'm assuming you used the Isky lifters with the cam?Can you provide any details such as what oil you've been using, initial camshaft break-in procedure, engine idle rpm, and the such. These may or may not at least give a clue to what caused the premature wear but it's a starting point in insuring the same problem isn't repeated.
Unfortunately, there are a myriad of reasons for a lobe to prematurely wear but the oil as of late seems to be at the top of the list. During the tear down, just insure that the lifter turns freely in its bore as that also comes to mind in this particular instance. Having worked with a multitude of rusty blocks, those lifter bores must be adequately clearanced or the lifter will not properly rotate and thus speeding up the wear process on the lobe.