I planted two tomato plants in my first garden and one has developed about a dozen green tomatoes ranging from marble-sized to 3/4 tennis ball-sized but the other, same exact species, has no tomatoes. There was one marble-sized tomato but I touched it with my finger and it fell right off. Is this a sign of nutrient deficiency or some disease? I do see some yellow flowers forming but they look limp. Interestingly enough, this is the taller of the two plants with no tomatoes.