Recent coil/misfire problems

[Muleears]

About two weeks ago I started getting the SES light. I had noticed that it was missing a little when started cold, I figured that was what was tripping the light. Foxwell told me it was cylinders 2+3 acting up. It always smoothed out after running a minute or so. Last week it was taking more time to run on all six, sometimes a couple miles. So I bought two coils and replaced 2+3. Put in a new battery about this time also. I should point out that the plugs were done about 6 weeks ago with iridiums. The new coils initially seemed to fix it, for a day or two anyway. Today when started to come home from work (a 40 mile trip) it was rough again and the SES came back. I drove it home but noted rough running most of the trip. When about 30 miles into the commute it smoothed out and began running smoothly on all six. When I got home Foxwell told me I had misfires on cylinders 3,4,5+6! These must have been intermittant as It wouldn't run on just two! So what I have done is swapped coils 1+3 with each other. #1 has never misfired according to the scanner, so now we'll see if the miss follows the coil or not. If the skip stays in cylinder 3 (with the known good coil) where do I go? Look at injectors? I only run premium and now it has a can of Seafoam in it. I'll report how it runs tomorrow morning with another cold start and 40 mile drive. TIA