Look to see if any of the schools you apply have specific requirements. If not, IMO it is fine to use one sophomore year teacher especially if you have a continuing relationship (my D did that with no issue). I would suggest you get your second teacher recommendation from a junior year teacher even if it will be a bit generic (ask the teacher if you can give him/her something like a resume or list of activities to help him/her write the letter) – a department chair who did not teach you in an academic class is not a substitute for a teacher LOR.