Also, how's your fan situation? To much breeze is another thing that can cause your tips to curl like that. I've been having better luck pointing my fan at the wall so that it bounces off, and gives a nice gentle breeze, at least with my smaller plants that size. Once they start getting big, and flowering, I find I can get away with an oscillating fan set back from them a ways. Just another potential cause that would be good to rule out.
Can't speak for potted, but I would say yes, a little longer between waterings, rather than less water per time. I use the Knuckle test, and with organic Nutes, or super soil, I water just till barely some runoff, then stop. Don't want to have the all nutes running away, unless they are chemical based, then do the whole 20% runoff like the Coco guys do.
I think your plants look pretty good otherwise from that pic, wouldn't really give it more Nitrogen just yet though, I think you could be close to having to much and causing problems. Theses guys having been doing this way longer than me though, so would listen to them if there opinion differs.
Good luck Getrich!