yellowing on leafs

Hey everyone, I'm having some issues with a couple of my plants. I'm not sure if this is excessive nutrients or is it a lack of nutrients? I'm using general hydroponics 3 part nutrient mix. I've fed each of them around 3 times. Each time, I watered/fed each plant with 1 gal distilled water...

Two leafs have this weired yellow on them, should I start feeding it nutes? I have fox farm ocean Forrest , the bottom two leaves ( you can see one 1 The picture) turned yellow and died off anyone know why?.... Iv been trying to get it to flower for over a week now on a 12/12 light cycle and...