I get to rank D and I get really happy. I start to level my stuff but then I miss a interview or something or my stuff goes down for some reason and right when my Producer Rank goes down as well as my Vocal/Dance/Visul stats, I have to go gainst my rival and I end up failing and not ranking high enough.
Well...
You can't miss an interview/stylist appointment/rival audition if you don't accept the offers. If you're not sure when/what you have to do for it, don't accept it XD I've never missed one, but I'm pretty sure that'll have a negative effect on your idol's career.
(basically...when the email inbox pops up in the morning, just ignore everything and close out of it)
Normal auditions are a really good thing to do, because when you win, sometimes you'll have a stat-boost from a blue reporter-person. It'll boost your stats for a few weeks.
I can't think of any reason your stats would
fall unless you missed an appointment, lost an audition (well...I think that's what those red reporters do), or you've gone for way too long without completing an audition.