Its impossible to say without knowing how you are growing m8.
Lights etc. What state are the plants in? All leaves green without yellow etc.
Post some info of your op and a pic or two of the plants.
Or check grow log section and try to see how other peoples plants develop. You are bound to find a few grow logs from people using a similar setup as yours.
If they broke ground from seeds on 28th august and look healthy it sounds quite ok though. The plants put a lot of energy into developing the rootsystem in the beginning and when they have a good rootsystem the growth generally just explodes.
I'll add two pics from my growth as a reference but every setup and strain develop a bit differently and I also had a problem with a poison hut stealing some grow time for me in the beginning but as a rough reference for ya.

Day 22 since sprouted:


Same plants exactly 10 days later. Day 32 since sprouted.

They grow fast he? I use 600W HPS and coco as medium and its White Widow.

Anyway, go to the log section and look for a similar setup and maybe you can even find one that grow the same or a closelly related strain in it.

Good luck

Puffzter