Paintstormstudio.com

I was playing around with the brush settings, and I had found a nice bristle brush I liked, but then it suddenly started making these weird marks. Before it had soft feeling to it but you could still see some bristles showing through, and now it has this really harsh look, while showing all the individual bristles (I guess). I tried enabling and disabling a lot of my different settings but couldn't find a solution. I also tried restarting the program multiple times. The strokes on the left in the picture are without bristles on, before the problem it was sort of a combination of the two. Also, GPU on and off didn't change anything.

Not sure that understand, but seems you just need to set "bristle diversity" slider to 0

I wonder if other terms would better describe what “Bristle Diversity” is doing?
Bristle Hardness? Bristle Contrast? Bristle Strength?
Probably not.
I do enjoy wondering what is happening when Bristle Diversity is set between 0 and 1, while color by linear gradient is on. Any setting over 1, and the main color overrides the gradient. It’s that sweet sweet spot betwen 0 and 1 that delivers the rainbow effect I love. Maybe don’t spoil the mystery. Just let it keep working its magic.

Bristle Diversity - gives brightness random shift to every "hair"/pixel which gives the illusion of a bump.