Looks like maybe ph has locked out mag or maybe needs more mag, really need a ton of info including any recent changes in environment. Rez temps, room temps day/night, RH%, ppm of nutes, ratio of npk and any changes to feeding....lots of info short of a home visit lol to really know whats going on with your plants. First thing I do is wait.....see if it gets worse....some times things go back to normal on thier own. Plants know how to fix themselves for the most part. If you do anything drastic right away it could get worse, alot worse lol. Change out your system like its the regular time to clean and redo the rez fresh and wait to see if they bounce back.....best advise I got bro