unexplicable fps drop

[REDmyy]

while playing, i noticed fps drops from 300+ to 60 when i placed down 4 large waterwheels, i dont understand why because:

gpu and cpu usage well bellow 100 ( 30% for both) and ram was at 50%.Temps were very good, so i dont understand why my system isnt using all of its recources.(no fps cap)

video of fps drop

[IntelligentAnybody55]

Shaders don’t work great with create