Laura, if your iris are growing, you can cut the foliage and they will
throw up new leaves in the fan. The fan that bloomed can, of course, be
removed from the rhizome, or cut waaaay down and the increases will continue
to grow if that's where you want them to remain.
Or maybe if the substance was merely paint or preservative, you won't get
any reaction from that, and your spots might be from something else. Rust,
Carolyn Schaffner in Bflo, NY