Lucky punk.... free wild nana.... :rant:
Actually, looks to me like either a calcium or potassium deficiancy. Check this site out (actually, memorize it, lol).
http://www.thekrib.com/Plants/Fertilizer/nutrient-deficiency.html#0
You can add calcium several ways-- you can bum a few teaspoons of kalkwasser powder from a reef-keeping friend (or buy a can of pickling lime at the grocery, same think, calcium hydroxide/hydrated lime powder), but beware that it will raise your pH, which nana likes anyway. Read up on how to mix and drip it into a reef tank. One or two cups of the mix (over a couple days) should give you quite a boost.
Or you can add some crushed coral to the gravel around the nana, but I don't think they absorb calcium by the "roots" but I may be wrong.
Potassium is cheap enough-- look for salt substitute, and get the brand that is closest to pure potassium chloride. Some add phosphates for stability, beware! Read the ingredients carefully! I forgot, though, how much to add, sorry! I haven't needed potassium in a while, my tap water is hard as a brick.
