I have my money on something toasted in the valve train. Take the valve cover off. Maybe you'll get lucky and it's a burned up pushrod end or rocker adjuster. Whatever it is, it's getting worse. Inspect everything VERY closely. If you don't find anything, fire the engine up and take note of how much each rocker moves. If you see one that doesn't move like the others, there's your wiped camshaft lobe.....which is what I think now it may be.
