Be careful about over wetting the carpets when extracting. You will fight a stain with the extractor and cause "wicking" which is:
Wicking is the upward motion of water and cleaning solution during drying from the base of a tuft to its tip carrying with it any remaining soil and contamination, which is then deposited on the tips of the tuft.
To reduce wicking, pre-vacuum thoroughly, make extra dry strokes, and use air movers.
The biggest cause of soil wicking is overwetting due to technician error. Soil wicking can be caused by slow drying, overwetting, overuse of pre-spray, and heavy accumulation of soil at the base of yarns.
Wicking is the cause of "reappearing spots."