It's getting low fps more than 1.15.2.

Put the summary of the bug you're having here

What I expected to happen was...:

What actually happened was...:
If I open a world, and wait about 10 seconds still 30~40 fps
and also, mouse moving is gets slow a little bit when you see a leaves.

Steps to Reproduce:
1. Put a step by step guide on how to trigger the bug here
2. ...
3. ...