Does your bird that lays smaller eggs have the same basic coloring as this hen? If not, she's not a red sex link...if she is, you got a bummer bird or something. My rsl always lay huge eggs that didn't fit in the carton.
I don't think you can go by that. It's completely possible to have RSL that lay different sized eggs. The majority of my laying flock are RSL and I only have a few that lay super jumbo eggs that don't fit in the carton. The vast majority lay a nice large to extra-large egg. We often have one or two that lay gigantic eggs, and one or two that only lay a large egg instead of an extra large egg. This holds true even if the birds are all from the same hatchery and hatched on the same day.
I've found that once you get used to a "normal" egg being an extra large, standard size larges look small. I'm always putting an egg on the scale because it looks so small, then having it weigh 57 grams.
How's your flock looking this spring, @donrae ?