Like Pom...I use Purex. I love the cost!!

I think the Tide stain you refer to might actually be something closer to a bleach mark. Perhaps the full strenght application discoloured the fabric. If this is the case, I don't think much will change it at this point.

But, you could try pouring boiling water over the mark and see what that does, or soak it in OxyClean for a few hours and see what happens.