08 Elantra weird ignition misfires

I've been having some problems tracking down a single cylinder misfire in an 2.0 Hyundai Elantra. It all started a couple months ago, driving down the highway started to misfire on 1 and 4, no big deal I thought almost 300k on the original coil so I replaced and all was good, fast forward a month, started getting a single cylinder miss on cylinder 3, checked and no spark at the coil, plugs and wires all checked out good, so I figured it was a faulty coil and replaced, now a month later getting a single miss in cylinder 4, Any ideas on what could cause single cylinder miss on a waste spark where 1/2 of the coil burns out? plugs and wires are fine. Thanks