Some questions:

Are the 2 lots the same variety?
Are they growing near each other and if not have you used weedkiller near the ones which have curled?
Have you checked inside the curled leaves for aphids?

I'm not sure I'd worry about them too much. They look as if they'll be o.k.

p.s. I'm interested you call them 'broad beans', like I do. I thought 'favas' was the name in the US.

They are the same variety- actually they are from seed from the supermarket bulk bin so i dont know which variety. No aphids. During heavy thunderstorms last year water would wash in here from under the neighbors fence, so there could be some herbicide residue from that I guess. Hopefully they grow out of it.
I'm from NZ, which is probably why I still call them broadbeans sometimes.
thanks

oops, i forgot to answer your question....they are on opposite sides of our backyard, and i've never used herbicide in the 3 yrs we've been here.

Well I've run out of ideas then. I suspect they'll will be O.K. in the long run.