The most obvious thing to look at would be the settings on your stereo, though it's unlikely that they got changed it's worth a shot. Just make sure that the fade and balance are centered. The next thing to look for would be a disconnection somewhere, either at the speakers or at the head unit. Is it an aftermarket or stock HU? If all connections seem fine you could take your one working speaker (or another you know works if you have it laying around) and test it in the other positions. If it works then your other speakers are the problem, if not then it's either the wires or the HU isn't sending a signal.

 

Yea I messed with the stereo setting which is how I figured out that only 1 speaker was playing cause I faded and balanced each speaker separately. Just took my one door speaker and plugged it into the other door where the one speaker is playing and the speaker is fine. I'm thinking an electrical issue somewhere, just don't know where to look. Doesn't make sense that 1 speaker plays while the others don't.

 

It must be either the speaker wires or the HU then. It seems odd that 3 speaker wires would all go bad at the same time, so my guess would be the HU, unless the wires somehow got disconnected. Have you removed the HU to check the connections?

 

I'm going to take the inside panels out tomorrow and check all the wiring and everything and see if I can find something. Will update.