Have not heard 90 days, 5 days after symptoms reside you are no longer contagious and can retest.
( 10 days after onset )

I tested positive after a mild case, sore throat on Friday (onset?) , positive test on a Thursday ( 6 days later) and negative test on Sunday ( 10 days later ) .

Positive 8 weeks ago.... As long as they test negative now, you should be OK.