Children struggle at reading for a lot of reasons. They don’t have the perspective to know that other people can see better or hear better, but they do notice when they get confused or scolded for missing something.

Do have each one’s vision checked, and check each one’s hearing, as well. I have a daughter who is tone-deaf who struggles to hear the differences in short vowel sounds. She's just not that clear at hearing the distinctions. I also have a daughter who has fantastic sight in one eye and terribly blurry vision in the other eye; she can read but gets very tired quickly when doing close work. There are lots of possibilities, along with the standard statement about boys: they see better things that are moving rather than holding still, and they are not the most patient creatures!

Maturity will help, but don't 'do nothing'. You should encourage and be a good example of enjoying reading. Better to keep a good relationship with each child than to compare them and make them feel slow.