I'm having this problem, too! I'm bouncing it as a 24 bit WAV file, and when I play the bounced track in Logic when I master it, it sounds fine, but playing through iTunes and SoundCloud sound super muddy. I'm mainly worried because even when I listen to the uploaded file on Soundcloud on other devices, it still sounds muddy, and I don't want it to sound muddy when other people listen to it. Should I just not worry about it?... How do people normally upload their music to streaming services with it still sounding normal?