A few months ago all my yellow brick road zoas closed. They stayed closed for weeks and died back, but then the surviving ones opened again. The odd thing was that the patches of yellow brick road zoas were spread around the tank in differemt spots and all my other zoas were fine. Now almost all of my spiderman zoas are closed. Even the ones on the frag rack. All the other zoas (including the surviving yellow brick road zoas) are fine. What disease or irritant hits zoas by type?