Ye are not straitened in us, but ye are straitened in your own bowels.
There is no lack of room for you in [our hearts], but you lack room in your own affections [for us].
Ye are not straitened in us, but ye are straitened in your own affections.
There are no limits to the affection that we feel for you. You are the ones who placed boundaries on your affection for us.
You are not narrowed by us, but it is by your own inner selves that you are narrowed.
You are not straitened in us, but in your own bowels you are straitened.