Thanks for your response
The Urchin in question has been removed but it was not dead yet i just put it in a hospital tank for now.
This was all of my own doing as i did a very dumb thing when introducing a PH buffer to my tank by not disolving the powder like product in water first but spred it out over the surfface of the tank water and when this powder hit the Urchin he fell off of a rock and started to produce a stringy mucas like web from him, this did go away but then i noticed that one of his legs looks like it was bare from its velvity texture.
My biggest concern is, does this kind of toxin satturate the live rock and will it go away with water changes or am i in for a big lose of rock and all else?