Hmm... I noticed that Haru almost always wears a bracelet composed of beads on her left hand, just recently. She wore this in their Osaka-jo Hall live, Rock in Japan 2013, Mezamashi 2013 and their live in Grand Front Osaka, to name a few. Also, her teeth are getting more aligned as of late. Good thing she isn't that uncomfortable to smile now unlike when she first wore those retainers. She'd make a good narrator too.
For Tomo, I noticed that she wears a ring on her right small finger, but she isn't wearing it anymore since their promotion of ENCORE SHOW. Also, her hair almost always covers her eyes/face when it's not tied up. I wonder how she deals with it.
For Rina, well, a lot have already noticed this, she throws her drumsticks. And when she speaks, she often begins with "Ano..." or she frequently pauses while speaking. She's also very competitive, at which is an opposite to Haru's somewhat noncompetitive nature. But serious Haru is serious! .uhuh.
For Mami, lately she's been improving her showmanship. And lately, since Budokan I guess, she's bowing to the audience before the start of a live.