Advice

I have 4 plants and limited light atm and was wondering when's the earliest I'll be able to tell their sex . I honestly don't remember how old they are lol and I'm open to any other feed back thanks

And they're all bag seeds I've saved

You can tell there sex after you switch them to 12/12. Some strains you can tell before flower but not all. Switch them to 12/12 and watch for pistils or balls.

If you veg long enough, you should get pre-flowers around the third node. But I never rely solely on that and usually wait to confirm in flower.