Noticed today when brushing the pool these few spots. There are about 4-5 thought the deep end all in the spot where the wall goes from a 90 degree wall to a 45 in the deep end hopper. From reading pool school it sounds like mustard because it is on the wall and it says pollen/dirt will not be on the wall but I really don't know. It is faint but if you look in the middle of the picture you can see a faint yellow color. Don't know if y'all can tell from this or not.
Here are my test results and they have not changed the past 2 weeks much at all.