Any idea what this could be? It isn't on a lot of leaves but I just noticed it last week.
Here is a link that might be useful: leaves
Whatever it is, mine do it too and it seems to be cosmetic rather than fatal.
then I can sleep well tonight. They just aren't producing a lot of flowers but it has been hot and very very wet lately so, who knows why.
Some of mine do that too. It only seems to be on the older leaves and doesn't seem to do any harm, though.