Can't tell you which one it is, might be able to tell from the flowers, but I can tell you that its suffering because it doesn't have enough depth of soil for its roots - in a tub, should be something that's 2 feet deep which is shaded from sun - they like their heads in the sun, but need a cool, shady, deep root run.

And no - you shouldn't prune it until early spring...but we need to know which group it's in to advise you how far back to prune it.