Looks kind of like a potassium deficiency due to the yellowing along the edges and between veins. What medium are you growing in? What are you phing the water to? It might not be that you aren't feeding enough, it could be that the ph you are watering with is locking out that nutrient. You want your water to be around 6.5 ph if you are in soil and 5.8 if you are in a soilless or hydro medium. You can be a little below or above that number but if you are too high or too low the plant cant uptake what it needs.