Dep on the Strain,I have two plants ,that are 21 days in and they have colas forming.But I have another strain same age along side the other two ,and that is just starting to Flower.
Before you do any thing else ,there are a few problems you need to deal with,Looks like you may have a few Nutrient problems,also really wilting.This is probably a root problem.
Get these sorted asap or your end weight will be effected ,it's hard for us to diagnose the problems you have with those picture ,looks like a root problem maybe boron and Phosphorus,but with lights on I may be wrong up load photos from phone ,with flash on minutes before the main lights are due on or just has they go off.
Growing indoors and out is a Learning Curve,that curve can become a continues circle of failure if you don't listen to those that have made all the mistakes and learnt how to amend them.
Don't take this post has me having a go,because I'm not .Im trying to help,even those that think they know everything still have stuff to learn ,we are all learning .But at least start of with info that will help you get weights ,that will make growing worth while.Im not talking about Greg green ,or the greenhouse guys post on YouTube ,they are a sham for indoor weights
The info you can get of here has long had your room is right ,you should be hitting nice quality end product .
Good luck tyke.
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