Make sure masks are only the neon green, red, and blue. Any other colors can affect how the mask appears.
Putting those 3 colors on their own layers could help or remove any other colors that may be in the mask.
Example below. Mask has a tint of orange right between where areas are connecting. I circled the areas that are more noticeable in giving orange, but that orange was outlining tons of the different colors, for them- it caused the blend point between the areas to be very off. whiter bits on the mask can also cause very off terrain blends.
