Less is more until they ask for more in no uncertain terms, then for an application or two, or maybe longer term, a little more is more.. Just want to stress the link between lock-up and pH to go along with that concept.. Only feed your plants what they ask for if they asked for it when their pH was stable/proper..
If pH was erratic/off when they start showing deficiency, get that fixed first, and see if they can find the nutes they seem to want by themselves.. Feeding to combat lock-up is a black-hole leading to nowhere good..