I have never seen it with hyphens (-), but more plainly as: not all is dandy. The hyphens probably indicates that it is used as an adjective. You can create an adjective from any sentence if you add the hyphens, for instance, "his attitude is holier than thou" can become "he has a holier-than-thou attitude. Dandy is a word that originated in the 18th century , I think. In my mind it is a typically British word. It refers to a man who pays a lot of attention to what he's wearing, some may say excessive attention. While some famous dandies are gay (for instance, Oscar Wilde), dandies are not exclusively gay, they are more like metrosexuals. The word dandy can also be used to mean excellent, both as a noun (something or someone is a dandy if he/she/it is very good or excellent) or adjective (someone or something is dandy if he/she/it is very good or excellent). Your sentence probably means, 'not everything is excellent', that is, 'something that is wrong', 'something that is not working out', or 'someone who is not at his/her best'.