Altering vanilla block functionality 1.18.2

I'm relatively new to Forge Modding and am currently working on my first "real" Mod. It adds different grass types, and each of them can randomly turn into a "drained" variant. While this works fine for my custom blocks, I'd like regular grass to also turn into a custom variant, basically adding a randomTick event to the block. However, most tutorials I've found for this are for older forge versions. So, I'd appreciate some help.