deficiency?

I think this might be a combination of things. It looks like you might have been feeding too heavily at some point because some of the burn looks like nute burn on the tips of the leaves. The rest of it I suspect is from heat and wind. If your plant is in the wind it can get burned and the heat doesn't help. The split isn't a problem, it can often fuse back together again, but some support isn't a bad idea. It also looks like you've had grasshoppers or caterpillars, keep an eye on them. You can give your plant BT to help keep them away.