My paphs do yellow their leaves considerably under HPS lights , a dose of Epsom salts(magnesium sulphate) normally corrects it very quickly.As for calcium i give my multi-florals a little bit of Fish,Blood & Bone fert so i don,t see the need to use any extra .I do mix about 10% tap water with the rainwater i use on my plants so this also should have a little calcium.
The yellowing seems to be a lot more obvious since i cut the amount of fert i use to about 1/6th to 1/8th strength(from about 1/5th) , probably not getting some much trace elements from the fert now.