As polishpollack said , you have a nitrogen, phosphorus, potassium, and magnesium deficiency 25% likely A nitrogen deficency results in pale plants, red stems and stunted growth. Rapid yellowing of leafs running up the plant is another sign. and magnesium is another big one lower leaves turn yellow and may turn white while veins remain dark green. Blades die and curl upwards. add some nutes to solve. plants should recover within a week.