I was trying to kill slimes and magma cubes, but i couldn't hit them over there eye, or even a bit lower. I have to hit them really close to the bottom. Its as if they are the small ones when sometimes they are the huge ones

What I expected to happen was...:
The I could hit them on any part of there body and they would take damage.

What actually happened was...:
I have to hit them close to the floor so they take damage. Higher parts of the body they wouldn't take damage.

Steps to Reproduce:
1. Find a slime or a magma cube. (Big size)
2. Try hitting them over there eyes or over the middle of there body.
3. They don't take damage in areas over around the middle of there body.