Volume lowering to about 30% Randomly.
 

Linux Mint Xfce 18.2 64bit
Keyboard: G710
Sound-card: Fiio E07K dac.
Mic: Logitech 615 webcam

No clue why, but the volume will jump from full down to about 30% randomly. No clue what might be wrong, although it might be related to an issue I had before were my Mic would disappear while using mumble. What might be causing this, could it be a security breach?

Which volume/gain level are you referring to specifically? Is it the Mic level?

Any applications streaming when this happens?

most likely a pulseaudio issue, i've heard about these before.
get familiar with your pulseaudio mixer gui, most likely pavucontrol.

pulseaudio has per APP mixer levels, if you accidentally triggered that it could be making that adjustment everytime you run that "app" and it accesses the sound card. If you're not too fond of your "settings" you could $(rm -rf $HOME/.config/pulse) and reboot / restart pulseaudio. Just be sure to use $(pavucontrol) before you start running sound apps to avoid per app unique-ness.

I've had it where the volume was adjusted in a certain application, and it would always go there even in other applications.