Ok 1st thing 1st check your roots. It looks to be mild but I can kinda see the yellowish pale green spots and Ive had my plants do that exact same thing befor. Whats your ph at right now? Have you calibrated your ph meter lately? After you check these simple things first then try the cal-mag. Get some close up pics so we can see it better.
Good luck
BigGreen
my roots looks ok.no root rot or something wrong.smells is no bad
and the water temps are 21c.
ph 5.6-5,9-i check it with 2 ph metres-
and some fotos.