It won't heal, but by keeping the pH and fertilizer level correct, you can keep it from getting worse, and the plants should recover.
Make up a foliar feed that is one quart of tap water, one drop of liquid dish soap, and enough 'grow' fert to make the equivalent of a 1/2 strength nute solution, and lightly mist your plants with that.
Foliar feeding is a good way to correct observed deficiencies while you are trying to solve the problem that caused them.