The yellowing leaves is most likely nitrogen deficiency and I see some yellowing between the veins on some which is the beginning of magnesium deficiency. I would guess that the rust spots on the leaves you removed was calcium deficiency. A high quality soil will feed the plant for about 3 or 4 weeks, but they will need some food after that. I would add a good quality stand alone nutrient at minimum to get them back on track. I am not much of a soil grower but feeding with every other watering is usually a good place to start with feeding times. I use general hydroponics maxi series nutrients just because of their simplicity and cost. Good luck!