Galaxy S4 music playback issue

[Mercify]

I have had my S4 since last July and almost everything has been working great. I got the Android 4.3 update and since then, whenever I tried adding new songs to my S4 via sd card from my computer, it says it can't be played. I tried installing another music player called Rocket Player and it said this file type cannot be supported for each song. They are all MP3s and I am sure since i checked. I tried formatting my sd card and put back in all the songs. I tried force stopping media storage and music player and cleared the data but that still didn't help. I even turned off my phone, removed the sd card, restarted, turned off, put back in the card, and restarted it. Still nothing. I saw online that twitter may even be the cause so i uninstalled that, but still nothing. I don't know what else I can do. I need help.