So, my pool is a little over a month old. This morning I went out and glanced at the pool but didn't see anything wrong. By 2 pm when I went out to swim, I saw this spot on my front step. My plaster guy said it was caused by the "cynaric" acid in the chlorine tablets and says he tells all his customers not to use them. Well, actually the care and maintenance guidelines from him say don't use the floats because if pieces break off of the tablets and land on the plaster they can damage it. I brought this up to the maintenance guy when he proposed using the float and he said it'd be fine since the tablets just slowly dissolve. Since it's Memorial Day, I have to wait until tomorrow to talk to the pool maintenance company. I guess my question is who IS responsible for fixing this? Is this stain permanent and is there anything I can do to make it less noticeable?