I installed the latest OptiForge for 1.16.4 and the compatible and latest OptFine. I realised that with SEUS Shaders, lava has the same texture as water, water and lava look identical, with only lava having some warm lighting around it. I know this is because of OptiForge because I launched OptiFine alone and lava looked fine.

Edit: Hmm.... nevermind, I removed OptiForge and just put OptiFine into the mods folder, and launched it with forge, it's still there.