Evergreen 4 in 1 stained my decking?! Please help

Hi
I have recently put down some decking! I then used evergreen 4 in 1 on my lawn! I then walked across the decking a few times & when I woke this morning I found black footprints marks on the decking! I tried washing off & doesn't seem to work?! Any advice really appreciated?!

Thanks
James

 

Before any advice can be offered we need to know what the decking was treated with.
@pete will probably be the most help on this.

 

This problem has been reported here before (with a remedy)

http://gardenerscorner.co.uk/forum/threads/evergreen-ruined-my-decking.54132/

P.S. Also posted here https://uk.answers.yahoo.com/question/index?qid=20090920113149AAGDwOK and here http://www.diynot.com/forums/viewtopic.php?t=176785 in the past without any recommendations for treatment.