suspected a vacuum leak but a whole can of carb cleaner revealed nothing except a bunch of pretty colors

fuel filters have been in for a month roughly, this problem is a few days old. started intermittently and is now almost full time. a little more reluctant to occur when the engine's cold but it's starting to happen anyway.
I looked under the hood in the dark and observed some lighting effects around the #1 and #3 plugs (and a little around #2, nothing around #4) and i'm sure they weren't due to the carb cleaner!
I'm guessing that my plugs aren't getting their full amount of juice for some reason but i'm not sure where to go next?