Leaky pvc ball valve handle cap and pvc joint
I have been in this situation a few times.  For the elbow you may have luck turning off the water, draining the line, then brushing the connection elbow to pipe location and around the elbow itself with PVS cement.  If you can get a flow into the leak location it may likely seal.  It is a fair possibility that a hairline crack or cement gap occurred.  I have had about a 60% success doing this.  

As for the valve leak I hate to say may need replaced.  One exception is if it has a handle that is held on by a screw.  Check the blue handle looking for the center disk to see if it has a gap to the main handle body.  If so see if it will pry off and has a screw to tighten handle to ball assembly.