Potato leaf problem

I am growing Rocket early pots in a potato barrel. The leaves have been covered as they grew in the normal method. The leaves are now at the top of the barrel and I am letting them grow on. Problem is that the leaves look a bit poorly. Bobbly and a little curly is the only way to describe them. Is this a symptom of a problem or do they always look like that (I haven't grown Rocket before) The later salad pots in the bags next to them look fine. Grateful for advice.

MD