No, the way it is now is alright, as:
1. Small rainbows won't be changing from Entropy due to Supernovas
2. They still could only use 1 mark, so not all of those cards in a rainbow, just one select element. You could call it "Water focus Rainbow" or something if it was using a Watermark to use an Ice Comet or something.
Also, the Nightmare card... well, what were you smoking while making it? It seems bad for the brain. It completely screws over any Darkness deck you'll be facing, but against all the other it's useless. How is this good?
Also, how do I steel quanta?
/sarcasm SPELLING. WORK ON IT.