A server I created on ServerPro has a lot of glitched blocks and textures

I followed this video to set up the server https://www.youtube.com/watch?v=pWcA0qTxcRg

There are many weird pools of water filled with coral, and the coral filling all caves, aswell as some blocks appearing wrong

Are there any simple ways to fix this issue?

From what I know, this happens when you join a modded server with a vanilla client. Please make sure you have Fabric installed on your client, as well as all the mods which are installed on the server.