first off, your gravity may have bit a touch low if you didn't get the efficiency that beersmith had for the recipe, adjust beersmith accordingly.
second, beer always looks a lot darker in the carboy than it does in the glass. SRM is based on the latter.
BTW, i just pitched my PM northern english brown about 90 minutes ago! i had the same issue, but the other way around. had efficiency set to 75%, got more like 80%! time to adjust the software! errors in my favor as i added a bit of water to hit the OG, so more beer!