Mobs Not Burning (Skeletons and Zombies)

The Mobs On My Realm Wont Burn During Day?

They Are Not Under Any Cover Like Trees Or in Water, They Just Walk Around in broad Daylight

Without Burning!

Please Help Me This Is Beginning To Be A Very Annoying Problem.

I Have Added Vanilla Tweaks To The Realm, I Don't Know If That Would Have Anything To Do With It? In The Past It hasn't?