20/4 is a pretty poor light schedule in my opinion. 18/6 is an ideal schedule for vegging plants. And you won't see a sure sign of sex until you switch over to a 12/12 lighting schedule, unless your plant has begun to preflower. Get some fans to strengthen their stems. The buds may turn out fine but more than likely they will be a little bit wispy and the weight of the buds may crack your stems and branches if they are not strong enough.
And RAS, what does the 7th node have to do with anything? lol
I've had plants working on their tenth node at 6 inches and it wasn't showing sex. To sex you need to change the plant over to a flowering schedule. Unless you have an autoflowering plant.