just noticed yesterday that the left side speakers (Front & Back) are barely audible. is it a blown fuse? or the speakers are blown?

would be nice to just get a new system, but low on the funds.

any thoughts to what this could be? i tried fade and balance, and it's just the left side. i first thought i blew the left front speaker, but discovered that the back left didn't work as well. so could it be wiring, blown fuse or something other?

any thoughts? thanks.