I recommend an enzyme carpet shampoo for the ground in areas.
your local pro carpet cleaner should have some.
I clean carpets professionally,
and if the pro can’t get it out, it’s permanent.
A lot of the ground in “brown” areas are probably from just normal wear, and there’s not much you can do about that except replace it.
If an enzyme pre-spray doesn’t do it, that’s it.
Thanks. I guess if the enzyme does not work it is time for Barabasol or Burma Shave.