digi,
I "assumed" you were going to say you used tablets... which would have meant that your CYA of 5 could not be correct.
But... If you are using liquid Chlorine, then a CYA of 5 is possible, but a major concern. Without CYA in your water, the chlorine will not last very long.
I suggest that you bring your FC up to 4 or 5 ASAP.
I would also bring your CYA up to 30 ppm.
I see you have been a member since 2014, so how do you normally test your pool water?
Do you have a pool service, or do you maintain your chemicals?
Thanks,
Jim R.