One of the biggest flaws with Difficult Life was how blights were marked by setting them on fire. In many cases, this is fine. However, blights falling into water could be put out. I fixed that by marking blights in their NBT and re-igniting them as necessary. That mostly fixes the problem with water, but some mobs are immune to fire, and can't be ignited at all!

I believe the best solution is to ditch the fire and spawn particles around blights. Blights are already being marked, so it will be easy enough... just need to choose a decent particle effect to use.

Thanks to mopsyd on CurseForge for pointing out the immune to fire problem.

Created custom fire effect instead.