Chemicals all in range, small green patch on wall

[KJB1]

I took my solar cover off this morning to check chemicals and brush and was disappointed to see a green spot on the small 10” deep section of pool wall on the shelf. It was bright green and maybe 3”x10”. It immediately came off with one swipe of the brush. I checked chemicals and all are in range. FC 5.0, cc 0, ph 7.6, cya should still be about 40 as I haven’t added any but 1 puck in the last month while gone for a couple days.
Should I worry? Water is crystal clear. I immediately added 32oz of 10% bleach and brushed and sent the robot to vacuum the entire pool. FC should be near 7.0 now. I plan to dump a gallon of bleach in tonight for good measure. Should I bother?

 

[mknauss]

Do an Overnight Chlorine Loss Test. If good, should be no issue. Keep FC at least 20% of CYA for today and tonight.

Water does look a bit cloudy. So be sure that clears up.

 

[KJB1]

Thanks. I’ll add another quart now and report back on the OCLT

 

[KJB1]

Chlorine loss is .5 overnight. Tested 8.0 at 10:15pm and 7.5 at 6:45am

 

[KJB1]

Forgot to mention, the water isn’t cloudy. We have had cloudy weather lately and in the photo it makes it look kind of off.