Well that blows my theory out of the water but I don't think it's blockage and what not that would mean that all three burners are blocked. They are the tube kind and are completly independent.
I grilled up some chicken tonight and broke out the level and it was the bubble was on the line. I stuffed some wood chips underneith the side that was low and that fixed it a little bit.
Didn't know propane was heavier than air, I failed chemistry miserably in High School.