in 1-gallon or less pots? with soil? probably rootbound and issues are inevitable. it likely has plenty of nutes available, if you have been feeding it regularly. pH is good... solutes are fine...
good news, you are still in vege, eh? pot up...in soil i'd go 5-7 gallon and bloom them ASAP when they recover.. if this is first grow, know they will double in size. if you got that stuff covered, nevermind.
If you can't get through grows without a multitude of supplements or even common to see deficiences, get a new fertilizer. Outside of my lack of experience with younger plants, i never have issues beyond minor blips with mature plants or in bloom. it's not because i have a green thumb. i stumbled upon a good product from a decrepit 2009? forum post (i want ot say his avatar was darth vader?), then found a youtube channel of some guy in CA that uses it and has a nice run-down how-to. i even used it in soil for several grows with zero problems. re-used the soil 3-4 times.
Maybe, you don't see this problem with bigger pots and it is equally perfect for you too.. but, if it's common, look for a replacement.