Janna's Passive
To put it simple, it's pretty fucking useless. I mean, it's only a 8% movement speed increase for allied champions that are within a certain range of her and even then it's only if they're walking towards her. As a squishy ranged support Janna is almost always going to be on the backline making her passive utterly worthless on her. Instead could you just make it where all allied champions get the buff as long as they're within range of her. I mean, Nami basically has her same passive but better. Even better you could add to it making it not only increase the movement speed of all allied champions within range of her by 8% but also make it slow all enemy champions within range of her by 4-6%, not to much but just enough to make a difference. Not to mention it would make her a lot more interactive and keep people who play Janna from just sitting on the backline and shielding their ADC, now they would have to participate in fights. Trust me, I'm a Janna main to, M7 and over 400k on her, and in the end all Janna really is is just a Soraka with shields and more CC.
This is just another idea but maybe completely change it to something more defensive based, like enemy champions near her have their attack sped decreased slightly or all allied champions near her have increased armor and magic resist. I still like the whole "all enemy champions near her are slowed" idea the best though.