At this point all you can do is water and hope for the best.

I would stay at 18/6.

Only time will tell.

No ferts.

Just water and light.

As for you sexing question, yes, you can do that....but many people say it turns plants hermie....though I have never seen or done this myself.

Another way is to brush some pollen on one stem...light it for 12/12 and when her 12 of lights is up, cover the stem with a thick black paper bag. WITH A FAN ON IT.

Or, clip a clone, root it and sex it.

Sorry to hear about your disaster....

Never met a great grower who didnt ahve a few of them

Disasters teach us good lessons.

Because......success leaves clues