Help problem with volume

im having an issue with controlling the volume in apps like youtube, facebook, or anything else that involves showing videos on my phone. i can hit the button to lower the volume to completely muted and its still loud as ever, not a difference at all. wondered if anybody else ever had this problem and if theres a quick fix for it. i just purchased the phone yesterday and rooted it, other than that i havent changed anything other than settings for facebook location. if anyone needs any other info about the phone ill gladly post it. LG optimus F6 MS500