Tom,
There are many molds that are gray, and then there's the tomato disease Gray Mold, caused by the very weak pathogen Botrytis cinerea, which is so weak it can only infect thru wounds in tissues and fruits of tomatoes. But it does have a wide host range, unlike most of the other tomato pathogens.
There's no way to know what it is you're talking about re a "gray mold" on peat pots containing herbs in terms of knowing WHAT gray mold it is.
If it bothers you I'd just scrape it off.
Peat pots are notorious for allowing mold growth on the outsides as well as on the surface of the mix in the pots.
I hate peat pots. There, I said it.
