Baby Happy Ghast does not grow up naturally

I was playing in a world with the tick speed set to 50, and I noticed that despite this the baby happy ghasts that I had were not growing up. I set the tick speed to 500, but they still stayed in the baby stage. I know that the tick speed was working properly, because I tried hydrating a dried ghast with the tick speed at 500, and it became a baby happy ghast within about 10 seconds. But none of the baby happy ghasts would grow up. The only way I could get them to mature was by feeding them snowballs, they would not mature naturally.