Without a TON of help with the picture quality, relying mostly on guesswork, I'd have to agree with red planaria (flatworms).
Do the red leaves 'dissappear' when lights go out? If yes, then this is another indication of flatworms.
If you can get us a better picture, you've left yourself a LOT of room to improve the picture, we can offer you a more concrete ID.
If in fact you do have flatworms, we can offer you ways to rid your tank of these pests, capable of reproducing in plague proportions.
Best of luck,
swimmer