When doing my treatments I always did them in a specific area (computer area).
Well when changing around the room (tan colored carpets) we discovered that the whole area was significantly more discolored than the rest of the room.
My grandmother cut a section out and took it to a carpet store and in the mean time tried everything to get the stuff out of the carpet.
Nothing worked.
Carpet store said nothing they tried worked either.
Moral of the story: Carpet was replaced a year ago.
Good luck to you though.
Quite honestly with mine it could have been anything from xopenex, tobi, pulmozyme, albuterol, to colistin discoloring it. If you do find something that works kudos to you.
*edited to say*
we'd also tried steam cleaning the carpets, didn't work, the carpeting people suggested doing plugs to the carpeting (taking little sections out and replacing them with clean sections of carpeting) but since this was from treatments it was pretty much all over the computer area.
After you've taken care of the problem see about getting some of those office mats to lay down in the area... like that you can roll office chairs on.. Probably prevent a lot of that from happening.