Baby sheep grow up in about 5 minutes

Are the sheeps on grass? baby sheep grow faster in the presence of grass because gracing the grass speeds up their growing

As said above, baby sheep can accelerate their growth by eating grass.

I spawned a baby sheep in a box and a baby sheep on grass and the baby sheep in the box took about 20 minutes to grow(the normal amount of time) whilst the baby sheep on the grass grew in about 5 minutes.

If you are reporting them growing faster while eating grass then this is a duplicate of:
MC-190735