When my brew boiled over today, I noticed the foam carried with it some grainy green stuff. When it dried, I looked at it and believe it is hops. During the boil, a similar ring of green stuff forms. What is this? Do I need to be stirring it back in? It looks like my hops is being lifted during the boil and sticking to the upper sides of the pot, do I need to be stirring that back in? I'm using pellet hops.