Landscape black material in mobile preview

Hello, why is my landscape material turning black? in my landscape material uses 4 layer, on 1 layer the grass works well on mobile preview but on 2 layer to 4 layer when I paint it turns black on mobile. That’s why? Sorry, I’m new to the Unreal Engine 4.26.1.
Below is the picture from the mobile preview:

331729-blackmat.jpg

Think I solved this. The problem is the combined size of the textures was too large. I shrunk all my layer textures from 2K to 0.5K and it’s appearing normally now.

Don’t suppose you ever got a solution to this? I’m having the same issue