Question about leaves

I just had a few questions abouy my girls. The new growth on the top of the plant when it starts getting bigger the leafs tips are yellow.
Is this a bad thing or not its just the tips and that is it and it does it to all the new growth. I have read a few things about this and dont know what is the truth
One of them is it is over fertilized, and the other thing is it is not fertilized enough. I have it in miracle grow soil which it says will feed about 3 months the rest of the plant is fine green and thriving I have not added any nutes at all since I started growing
Just wanting to know what I should do or not do . Thank You for the advice ahead of time...