Are they both sucking one side? Can you put the bigger on the full side a few times to help reduce the size, get one used to it and make it easier to suck. It may just need a few days to settle.
I've got a first timer who kidded twins last Tuesday, the boy bigger and gaining weight a lot faster than the girl. The doe has one side very full and the first two days I took a pint off each day to soften it, the girl is sucking that side now.
She may have had an infection in the teat canal after last kidding that narrowed it slightly, assuming the milk comes through ok it should come better, just watch carefully for mastitis.good luck with the rest.