Raise FC immediately! For CYA of 40 you should shoot to maintain 5ppm FC.

Also, you might want to lower pH a tad (shoot for 7.4-7.6) using muriatic acid (31.45% concentration, not the low concentration "safe" stuff).

My only experience is with a vinyl pool, but if I understand correctly, with a concrete pool you'll want to raise CH to at least 250. Hopefully someone with more knowledge of concrete pools can chime in.