Is a low Cal a problem for a vinyl pool?

P234 results
FC 3 (but I just added a jug of bleach or 1.7 PPM)
CC 0
TC 3
PH 7.4
Alk 100
Cal 20!!!
Cya 40
Temp 80

I hadn't measured Calcium hardness in a while but I was quite surprised to find it that low. I had been battling iron stains and have added some heavy doses of iron/mineral sequestrant. Otherwise it's been BBB (Tri-Chlor earlier in the season until the Cya got to ~40).

The pool looks good. The water is clear and the iron stains are gone (for now).