If you have them in a very sunny and warm spot, sure. I would also give them a little balanced fertilizer to speed recovery before frost. If they are growing in the cold, rainy North, though, they may not win the race!

If you go to the garden centre they have an array flower plant liquid fertilisers as we know ,but a lot of advice given is to increase flowers by just using liquid tomato feed ,you could try cutting back gently and if you dont already switch to tomato feed as surfina are hangers it would look better the flowers hiding the leggyness.