Terrain paint blocky

I am trying to make a section where it looks like snow is melting but no matter how light I try to make it it always comes out as a big block around.

I found the reason this is happening, but not how to fix it. On 4.16 the terrain is locked at about 1/4 the resolution (1K vs 4K) as it was on 4.14 which I could draw a perfect circle on.