Do the left side bulbs that flashed when the hazards were on light up to
full brightness when the turn signal is activated?

If the rear does not light, you probably have a bad turn signal switch.
Try jiggling it in an attempt to get the bulbs to flash.

If one lights dimly, you probably have a bad ground to that bulb.

If thay all seem to operate normally, try switching them with the right
side bulbs and rechecking right and left turn signal operation.  If the
problem moves to the right of the car, you've just found a bad bulb.