I don't know who's limiting lettuce, unless it's to the 1 cup or so of veggies that pigs are supposed to have per day. You shouldn't overfeed veggies. Hay is far more important to their diet, and if they come to prefer veggies over hay, then you've got a problem.
But fruit has a lot of sugar, and should be limited to only a small piece as a treat, occasionally.
Other than that, it's not an exact science. Some carrot chunks are pretty big, others are smaller.
Don't overdo the cilantro. It's like romaine lettuce -- some pigs will have calcium problems with it, others won't. Pay attention to their urine, and if you're noticing a lot of white spots, then cut it out.