Don't know that the cause is. everything is within range
0003 doesn't change the color at all (it used to a little previous seasons and one drop of 0871 would clear it. but this time 0003 doesn't change the color at all it stays clear)
my cya according to my tests with 2 new 0013 is less than 35.
I shocked my pool 2 days ago bringing it up to 18
Right now my FC 4.5 and I have some green and brown (dead algae?) spots that can be wiped off by fingers.
I've been using BBB for a few seasons now, never had this issue. My CYA was very low when I opened this season and this was the first time when I had to raise it.
I believe my CYA was around 50 previous seasons because i used to keep higher FC levels and I wonder if I should keep it at around 50 to avoid this issue?
My CYA tube is about 5 seasons old. Should I get a new one?