I'm not sure if this happened or just me imagining things, but...
I usually run my brightness around 75% when plugged in and started to notice that my display was running a bit dim for whatever reason. I didn't do anything about it however.
A few weeks back I realized my battery was bulging as my trackpad wasn't clicking properly, so I replaced the battery, and did SMC and the other memory reset.
Pretty sure those controller resets corrected my brightness issue, but again, could just be me imagining things.