Yeah, me either. I've never owned a puck. If you've been running the pool since 2014, or longer, on TFPC and this is the first time you have had this issue then it is very likely organic. So keeping your chlorine elevated should clear it up.
If it is white and rough then it could be calcium scale, filling and keeping your CSI negative -0.2 to -0.4 for a while, weeks, and brushing will put the scale back into suspension. Then keeping your CSI negative -0.1 to -0.2 always will prevent it in the future. Poolmath will give you your CSI score after you input your test results. CSI is managed by tweaking PH and TA.
Do you have hard water?