Extreme lag spikes in sky island

Ever since I've been playing, I experienced really weird lag in the sky islands.
My specs:
i5 9600k
gtx 1050ti
8gb ram

Whenever I'm not in the sky I get like 200 – 300 fps and inside the sky islands I have like 400 fps, but my fps very commonly spike down to like 5 fps and then jump back to 400. And yes, I am using optifine and wynntils.

I saw some other thread about this exact same topic and the person said they added something to their JVM arguments to fix it, but I have no idea what they added.

pls anyone help me i want to lootrun there but i dont want to lag myself into the void and die

 

use Phosphor (a performance enhance mod). idk anyone else but it fixed the problem for me by a quite a bit
https://www.curseforge.com/minecraft/mc-mods/phosphor-forge

 

Wow that actually made it way better. I can still feel some lag but at least its playable now. ty

 

can phosphor and optifine be used at the same time without any issues?

 

if you want optifine for the capes you can use this
https://www.curseforge.com/minecraft/mc-mods/optifine-capes

as for other performance improvements... there's a bunch of mods for that