Stains around the brush, when using soft brush

[Ila22620563g9f7]

I have those weird stains around brush- when using soft brush. 

[D Fosse]

That's banding. Banding is caused by insufficient bit depth.

If you're working in 16 bits in Photoshop, any banding you see is in your display system, which operates at 8 bit depth (unless you have an expensive 10-bit capable monitor). A defective monitor profile, calibration tables in the graphics card, a bug in the GPU driver, or a defective display panel.

Banding is cumulative, so any of these may add on top of each other.

[Ila22620563g9f7]

Thank you for your kind reply! my monitor is not the best one unfortunately, I work in 8bit mode, I have two monitors and it apears on both of them.