Icons showing in Hover state when they shouldn't

Hi there

I am relatively new to the eLearning developer role and am really struggling with some icons that are appearing in my 'hover' state when they shouldn't be.  

My enquiry relates to storyline 3.

Basically I am putting information icons on a layer, 4 in total, each of which I would like the user to be able to hover over individually and in the respective hover state I only want the learner to be able to see the icon over which they have hovered (and the associated information I have added).  But what is happening in the hover state is that it is showing all 4 icons.

When I go into edit the hover state, I only see the icon I want to see, but it is in preview that I see all 4. 

I have tried going over the additional icons by putting a shape box the same as the back ground over them but it doesn't work.  I have tried converting the icons to images but this also does not stop it from happening.  

I have noted that it seems to be affected by the sequence of when the picture/icon (doesn't matter which as they both are doing it) is added to the timeline. For instance, when viewing the hover state of the picture at the bottom of the timeline, all the ones above appear in the hover state, (even though they shouldn't). But when I am doing a hover state with the picture at the top of the timeline, it doesn't show any of the icons/pictures below it. As for the pictures in the middle of the timeline, they only show the pictures above it when in the hover state.

Please help - it is driving me nuts!

Many thanks

Emma