Well as the hair grows it gets a little weight to it. Who knows really, it could be a lot of factors,

Maybe your hair is all 4a and youre growing scab hair out which looks to be undefined,

Maybe your hair is just adjusting

Maybe youre using something

Again, it could be a lot of things.

Im around 98% 4a and the rest is 4b above my ears. When I first started my hair looked like this.

and then this