First Timer - Quick One

I wouldn't worry about the green stuff growing on top of the soil... I WOULD worry about two things: 1) 50F is far too cold for the poor thing, especially if you've got 60% humidity! And 2) you're overwatering her badly and this will kill her faster than anything else. You've got to bring your temps up to the mid-70s at least and you've got to allow the soil to dry out completely before giving her another drink of anything. The heat will help the soil to dry, too... The humidity you've got is ok - it's just the temperature that's really, really bad... Your worries about being too acidic is kind of off the mark here... You're not recording the pH of the water you're giving her - perhaps you're not measuring it? For a soil grow, you want to keep the pH between 6 and 6,5 ... 6,8 as the highest... Good luck! Warm her up, let her dry out, you should be good!