Drop check multiple layers

Hello,

I have had a dabble with storyline in the past and have just started my first project, having some difficulties with triggers. The project aim is for a learner to connect up multiple components of a system, I am achieving this by changing the 'wires' state from hidden to normal when an object 'Orange Oval' is dropped on the corresponding connector, once dropped the 'Orange Oval' is also changing to hidden. I am wanting to advance to the next layer when all 'Orange Ovals' on that layer are hidden. At the moment i am overcoming this by adding a 'NEXT' button.

I am also wanting to check the wiring and inform the learner if this is correct or not, I have tried to change multiple variables to true on each layer if that layer has been connected correctly. Then when the learner clicks the check button this would display as correct if all the variables 'PSU','ACU', and 'BGU' are True.