I had 6 with the same concerns this past cycle. I ended up using the science ones and 1 MD for almost every school and the rest depended on which activities I listed as my most meaningful and how I felt they viewed me. Not sure what the general opinion is but those I was working with said if it’s marked meaningful you should have an LOR from that activity if possible. So I’d say initially look at the requirement for the individual schools and then look at which letter combo can give the readers the most diverse perspective of you.
