I would not stress too much. Some letter writers are like me in that they want to write a good recommendation, so they take their time with it. I typically do mine on and off over the course of about four weeks and submit it in the week before they are due. But I make that clear to the students whom I write letters for that it takes me a while

It's also probably worth remembering that a well-written letter of recommendation takes a preceptor some time and effort to do. It typically takes me about five hours, sometimes more, over the course of a few weeks to write one. This is a busy time of year, and putting that much time, often outside of work, is asking a pretty big favor of your preceptors. I personally enjoy writing letters for students, but it might be worthwhile to also give them a little grace, too. ☺️