I've been lifting consistently since January (intermittently before then). I was fencing for a while (had to give it up because it wasn't working with my schedule) so that could possibly account for some of the difference; all the bladework was with my right arm while my left would just lay limp behind me.
So, for the most part, I'll just keep doing what I'm doing. I've been doing half my reps with arms together and the second half individually, so I can just make sure I'm working them separately the whole time from now on.
I know my muscles are developing slowly, but I just wanted to pose the question just in case it ended up becoming a larger problem later. I had some male body-building friends in college and I remember that one of the categories they were critiqued on was symmetry. I'm not exactly planning on competing, but I'd like to lift as if I am. Especially now that I'm getting even closer to my goal weight, my focus has shifted a bit from "getting the fat off" to "putting the muscle on." Lifting is the only part of my workout that I actually enjoy, whereas cardio is more like a necessary evil.
Thanks for the advice, Mel.