That looks more like browning to me and it's most often caused by using either a too high ph rinse or pretreatment and leaving the rug too alkaline ph. I like to leave it near neutral or a little on the acid side. You should use products approved for wool or this will happen again. I think that can be corrected possibly just by rinsing again with an acid rinse or picking up a browning solution. A lot of times the browning solution or a good acid rinse will give instant results. Real browning is always a ph issue. Most suppliers will sell browning treatment. I'd prefer one that is citric acid-based for that. Both my rinse and my browning solutions are citric acid. I normally use either a fine fabric shampoo on wool or a lower ph upholstery prespray that is also safe for wool. I follow with an acid All Fiber Rinse, usually Matrix from Jondon. Wool generally cleans up easily and with very little problem with the right chems.
You can also mix a little of an acid rinse up in a trigger sprayer and lightly spray the browned areas and brush it in. Follow by acid rinse extraction if needed. Dry with fans or outside if weather permits.