Problem with grasstype

Hi , i’m using the landscape grass type tools to spawn grass on my huge landscape .
So far so good it worked well, i’ve added 4 version of grass in grass layer, some rocks on rocks layer, some branch in branch layer , but now i’m in mud and i want to add some stuff too, the problem is that at some point, the new foliage that i add is no longer renderer in my scene . Is there a limit to the layer numer , or to the number of foliage i can spawn this way ?

thanks a lot , have a great day .