Recently I noticed one of my recessed cans flickering off & on. Now I have another flickering which is controlled from a different wall switch. It's not the bulbs or the wiring at the can so it must be at the wall. This is how the wall switch controls the lights . Three on/off switches at wall control: 3 large cans, middle large can only, and 4 small cans. There is another single wall switch on a different wall that turns the 3 lrg. cans off/on. I have not checked the wall plates wiring, what would I look for?