I went back and did the second bachelors too- all of my letters came from that time period.
1- more current info on maturity/character/abilities
2- I went to a bigger undergrad the first time; so while there were a few professors I felt would know me, I wanted my letters to be stellar. And with a few years distance between me and undergrad, I didn't know that I would get the kind of letters you need for admissions committees. You want your letters to stand out, especially when schools are getting thousands of apps for 150-200 spots.
Have you stayed in touch with any of your professors?
Good luck!
