Middle Arm on GE Dishwasher - cleaning

[lindajc]

Hi all - I've had a problem with my dishes not being clean after a wash cycle. I've done some cleaning of the wash arms and that has helped - the worst was the middle arm. Looks like water is coming into the dishwasher and is draining properly. Now, when I open the door I can see that the upper and lower arms are spinning, but the middle arm isn't. Water appears to be draining out of it. The middle arm spins if you push it manually. So, is the middle arm supposed to spin during the wash cycle? Should I be able to see it spinning when I open the door? I'm assuming that the force of the water going through it would cause it to spin... Would my next step be to take it apart and make sure that water can pass freely throughout (including through the conduit)?

TIA

Model GLD6300L15BB