Are these Substitute Sounds Normal?

by Lilis
(Australia )

Hi
My daughter is 3 years & 8 months old.

She often substitutes br sound with gr, eg. Brother - grother, bread - gread. Also pr to kr eg. Princess - krincess, pretty - kretty.

Then she also says tan instead of can. If I ask her to repeat after me shw can say them correctly, but she doesn't do it naturally.

Is it because she's just got into the habit of saying them the wrong way or she has a problem and needs help of a speech therapist?

Thanks.