Ignition switch would kill all the dash lights, not just the ones you mention(they're on the same circuit in teh switch), so you can rule that out.

I would say its probably a simple ground problem given the lack of predictability and relatively focused effect. Check the grounds on the relay board (row of poles with all black wires connected to it) and check the other grounding poles in the dash. They're all over the place, so hopefully someone with more knowledge about the specific ground of taht cricuit will answer. Maybe just trace the wiring to an affected unit and tighten items in its path?

good luck,
rt