... threw some dielectric grease and the end of the spring on the coil plugs...
How much is "some"?
True story: I put a "squirt" from the CRC bottle:
into the bottom of each boot. Starting immediately I got symptoms much like yours. The grease liquefied from the heat and coated the plugs, and gave a nice ground path down the plug. Not good.
Cleaned it all up and ran fine. So no, it was not failing coils: ran fine before grease, terrible with grease, fine after cleaning.
New coil boots come with just two or three tiny dots of grease in them. Does not need much to prevent adhesion.
Just my experience, FWIW.
Your coils are, I believe, covered by the extended program that Joe repeatedly informs folks about. If you do have one or more bad coils, your friendly dealership will diagnose and replace. If you don't, they'll happily charge you the diagnostic fee. Also, it is VERY HARD to do a proper coil test at home.
I'd say: clean all the grease up. If it's still bad, take the document to the dealer and get 'em tested.