Our neighbor who has the same Stonescapes mini pebble as we do, is seeing a couple of small rust stains forming on their baja shelf (Ranging from the size of an eraser to the size of a dime). It is not rebar as the shelf was blown with pure shotcrete. I told them Id post the question on this great website. My guess is that a few small pieces of metal might have gotten into the pebble. What could it be and is there a easy way to fix the issue?