Creeper only causing 1/2 heart damage

I first noticed this a few days ago while creating a 1.8.3 Spigot Server with a map that I got from a seed. The creepers can walk right up to you and only do 1/2 heart damage or none at all with no armor on. I tested in sp worlds and same thing happened when I got the map with a seed. If I just randomly created a world the creepers would do normal damage. A few times it only did 1/2 heart damage, but that only happened a couple of times. I moved to one of my laptops and the same thing happened when I created a map with a seed. ASUS NOJK-DB74T Gaming Laptop 4th Generation Intel Core i7 4710HQ 2.50GHz 16GB Memory 256GB SSD NVIDIA GeForce GTX 850M 2GB GDDR3 Win 8.1 Jave ver 8 update 45