For 5 – 7 pound rabbits, it’s usually recommended that they get a total of 1/4 cup pellets a day. Are you feeding a total of 1/4 cup pellets twice a day to be shared between your two rabbits, or is it 1/4 cup per rabbit twice a day? If each rabbit is getting 1/4 cup of pellets a day, that shouldn’t cause a lot of weight gain, unless your rabbits are getting less exercise than they used to. If they only get 1/4 cup of pellets a day and get plenty of exercise, but they are gaining too much weight, then you probably do need to cut back a little. Sometimes rabbits can put on heavier coats in the winter which might make them appear larger, but you say that they feel heavier too. The only way to know their weight for sure would be to take them in to the vet to be weighed, but you probably don’t want to make a vet trip just for that.
Unlimited hay is always the right way to go, and the amount of veggies that you are giving them sounds fine.