"On fleek," which as you pointed out means "on point" (another slang word, ultimately meaning that something "looks good" or "is executed well.") really only became widespread about a year ago or so. It is mainly used by young people. Although, as with most new slang terms, grown-ups use it in a slightly sarcastic way almost poking fun at the term. I believe the original context was, "eyebrows, on fleek," which means, "(my) eybrows are looking really good." Given its slangy nature and the fact that "fleek" isn't a "real" word, it has morphed into a general term to mean, "cool." "That jacket is on fleek." "Your hair is on fleek." Note that this word is really slangy, and a lot of people still aren't aware of it. I would not say it is in general circulation among the population. The most I've ever used the phrase is here, in this post.