First off...welcome to the site!!! You took the ribbing about your wattage to plant ratio in good stride.... you'll fit right in here
You said 3 x 3
CLOSET ... The word closet makes me think you mean 3' Wide by 3' Deep? If so what is the HEIGHT??? The reason I ask is if it is a standard closet it is too small for 18 plants.... but I'd hate to see you pull any before you know which are females and which are males.... Is there any way you can put in shelving to maximize the space while your plants are young and not so big?
Here's a picture from
Farm Friend's grow room to give you an idea of what I mean:
That kind of shelving comes in all sizes .... I have one in a small closet myself. You can see how she has the lighting hanging from the shelving. If you can put something like that in your closet then you could bring all 18 along for a while... perhaps until you get some pre-flowers so that when you do have to pull some... it won't be the girls
When you get ready to flower you can pull out the shelving.... and keep your strongest 6-9 girls .....hopefully you get that many.