Bump!!
I'm having the same issue with mine. The plant is 10 weeks old, one week into flowering (12/12 schedule with a 400w hps), and the upper tier leaves are slightly curling under. Its in a 5gal pot, MG organic soil (which I do not recommend!! Comes fresh with gnat eggs and your very own shroom spores...), I water only when the upper inch of the soil is dry. Leaves are all still very green, but a few look slightly wilted along with the curling.
I'll have to snap a few shots when I get home... but was hoping someone might have a little insight before then.