Modify two wet presets (pattern brightness for stronger density)

Follow-up a review of the commit 5f6e5425ae53a5bb1da62ee329866d81ae62a664,
(Tweak spacing on a few brush presets so they perform better on Windows)
Two presets lost a bit of density for performing color mixing. By lowering
the brightness of the flat texture, they both recovered the same density
of mixing while keeping the new spacing for performance on Windows.