On my way to OSH I was chatting on 122.75 to two Harmon Rockets over Missouri when one called out low fuel pressure on his mechanical pump. He hit the boost pump and no joy. 5 mins later he calls out his tanks are "sucking in'

. I did not hear what happened until I was tying down my plane and 2 Rockets taxied by. I walked over after they shut down to learn mud dabbers had nearly runied their day. Both tank vents were plugged.