It could be mustard algae. What other site?
Your solar cover should not have anything to do with your circulation, though.
If it is algae, your chlorine levels have not been kept high enough to clear it. (Yesterday you noted that your free chlorine reading was 1.1.) This is the reason for it's return. Maintain your chlorine at shock level as consistently as you can and brush the pool while the chlorine is high. Also, run the pump 24/7 while you are trying to clear up the pool.
Hopefully, your K2006 will arrive quickly. In the meantime, see if you can get a cheap OTO kit at Walmart (red and yellow drops). It will only read chlorine levels to 5ppm but you can use this color chart to interpret darker colors and their chlorine level estimates. This will help you maintain the 20ppm shock level that you need until your K2006 comes in.
http://pool9.net/oto-chart/
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