Landscape - 1 of 4 layers with low res / pixelated

Hi guys, first time I got this type of problem: 1 layer (blue color) of the landscape material are pixelated, all the other layers (gray/dev texture, green and orange) are fine, as you can see on the image below.

I dont think is the landscape resolution or texture resolution, cause both texture image have 2048x2048, and the other layers are fine.

All the layers info are “Weight-Blended Layer (normal)”.

I also try to use different “white texture” for each of the layers and got the same result.

Also try to use only const3 instead of a white texture + const3 to tint the white texture, and with only const3 for the flat colours without the Landscape Coord node, all layers got pixelated, except the “Dev Texture” (the gray one in the top of the material).

Anyone know a possible fix for this?