wats that def..iron?

new leaves got very light green and thinned.and whole plant got light green.they are 5 week old growing outdoor..thought about iron def but not sure anyway..

Outdoors in pots or ground?
What dirt & nutes?
I'm just going to take a
guess at this! I'm thinking
you haven't feed'em! And you
need to feed a full dose of veg
nutes! If you fed'em I'm guessing
wrong!

in pots dude.of course feeding them,using hesi nutes.dont know the dirts no ppm meter yet.watering with ro filtered 6.8 ph with epsom salt suppliment.but if you say that way,made a flush like 10-12 days ago.that can cause the problem?have 3 other plants doing well.or 6.8 enough for a lockout?