Switch icons back to default.
In usr/share/icons/numix-circle. Open up your index.theme file with text editor
A few lines down there will be a line saying
Change it to say
In the tweaks panel, select Numix Circle
now numix theme will apply to both plank and sligshot menu only. indicator and pantheon icons will stay as default.
(this solution was given by Adderbox76 in reddit )