Blur a few layers

[alberto fuentes]

Im making a video where I have up to 9 video tracks layered on some points.
Id like to blur at least 6 of them which have their effects and transitions
and play with the other 3 on top

When I blur them one by one I can still see the outline of the layers,
which is not bad, but not what I intended it to look like

I tried a few things, but without luck Is there a way to blur them all?
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