Hi all.
I just wondered if anyone can offer advice on a situation I've got with some stair carpets.
I do alot of work for a family and one of the jobs was to clean the stair carpets which had some stains on them.
The outcome was pretty good and the customer was pleased too so I went on my way.
Several weeks later the lady rang to say the stains had re-appeared. She wasn't complaining and would pay me to do them again.
When I went back I couldn't believe my eyes. The picture below gives you some idea why

These weren't the same stains that I had removed previously. Fortunately I purchased a camera for work and take alot of before & after photo's, so I was able to compare them and confirm they were fresh stains.
The lady was fine with this and once again she was happy with the results.
Today, however, about 3 weeks on, she has sent me a text to say....they're back again

, not as obvious, but wondered if I had any suggestions ?
Apart from setting fire to the carpet, I thought I'd just ask you all first, Has anyone any idea what might be going on here ?
I did lift the carpet to see if the problem was underneath.... Not that I could see. Also I made certain to not overwet the carpet and even towelled it off by hand to leave it as dry as poss.
Any other suggestions welcome

Les