render pass problem

[SgWRX]

so when i render out using mr passes, all my passes look great, but then when i merge i get this odd problem with my hedges. they are a scatter object. it only happens when i merge the building behind them. if i render just the foiliage pass, fine. if i render another building in the scene, fine. it's just when i merge the building behind these hedges. i've delete and recreated on a new layer, same thing.

 

any ideas? thanks.

 

EDIT: the odd problem is, it appears as if i lost 1/2 of my leaves. in the other renders they are thick and you can't see through them.