Painting specific Foliage type cause fps Drop

So I just replaced my old Grass mesh with a new one, and i started painting it as a foliage type ( with the exactly same foliage parameters of the previous model,and both uses speedtree wind) in new areas of my level, i suddently encounter Massive FPS drop while painting it making the painting process of big areas pretty annoying. The issue there is that the new mesh is even more optimized than the previous one (less overdraw and less poly) thats why i can’t figure out which kind of mistake am i doing.
Any suggestion?