When you are doing your sub-I in what you are interested in, and the dept knows it, they expect that you are going to ask for LORs. Do your best and really gun (not to be confused with gunning) the rotation. To Gun means going full force - Read up but don't show off obnoxiously. Know whats going on, ect.
The reason its hard to Wow people in 3rd year is bc you are learning the ropes - even toward the end because the rotations differ enough in the day to day goings on. You will be familiar enough with "what is expected" of you to do to WOW people as a fourth year.
A side note, all nose to the grindstone really stops after you get the LORs. You get off to interview, get treated a little better by everyone, and no shelf exams 🙂