OK so my GPA is right at that cusp ... it is 3.35, and my BCPM is 3.5. I've had interviews, but no definitive luck so far. Would you think in my case that I made a mistake in not mentioning a sentence or so in terms of that? In all other respects I have a strong PS, I should add.
The real reason is immaturity and overloading my semester schedules waaay beyond the limit thinking I could make it work, so it's not like your case where you had to work and that was understandably difficult. Oh God, tell me I didn't screw myself in this process. I'm just worried because all of a sudden I've been hearing from others (other applicants/former classmates) and reading in admissions essay books that it's almost expected to do this.
if you must mention it, be very brief (taking all responsibility). you want to demonstrate maturity, not blaming circumstances.