Am I supposed to be using like distilled water? Or purified water?
I like source water to be under 150 ppm's (parts per million), some tap runs crystal clear and some are upwards of 500ppm. You'll have to buy a tds meter to know what your ppm's are, they're cheap. What I did for a while was used 18 cup water purifiers that you would keep in your fridge for drinking water. Try to keep your ph about 6.2, you'll need to buy a ph meter, they're cheap.
Over time from giving plain waterings your nutrients within the soil will diminish, and the plant will likely use/require more nutrients as it gets bigger. So there's not much you can do except wait. Your plant isn't dying so you wouldn't want to flush it.
Don't top if you've already started 12/12. I would give atleast one week recovery after topping before I even flip otherwise you're hurting your yield.
Very important that you don't disturb the dark cycle during flower or the plant will hermie(some will herm right away, some arent as finicky and take more to make herm) and be junk.
You can expect anywhere from about 8 to 11 weeks flower for harvest.
Look for a grow bible, those will help you a lot, the cultivation of cannbis can get pretty complex.
Also, how much room do you have left before that plant grows within 12" of the light when the lights hung as high as you can get it?