Ok, this is all starting to make a little more sense now. Please explain what is and what isn't hydroponic about your system. If it is just the amount and timing of your watering then yeah that's the problem in a nutshell. You are treating them like potted plants.
The difference between growing in soil and growing in a medium where you add nutrients (hydroponics) is that the soil provides a bulk of the nutrients and you water to provide hydration, oxygen, and then amend the soil with smaller amounts of nutrients. The plants and natural biotics in the soil will break down the nutrients in the soil.
With hydroponics, you are giving them everything they need to sustain. You can't really water them once or twice a week and hope they get the nutrition they need. You need to feed them more often (like twice a day) for them to get what they need. Otherwise, you get what you got.
To use the cooking analogy again: Think of growing in soil like beef stew and hydroponics like making a consomme. With beef stew (or soil) you have a bunch of flavor enhancers built into the soup. You add some water and a little extra flavor and voila, you got soup. A little too much carrot, no problem. Not enough onion, no biggie. With consomme you need to provide the flavor, and if you go overboard on anything it will show. You need good water, a light touch on the seasoning, and a handle on technique.
So again, if you are only using the cococoir as your medium, then you really need to be watering and feeding them constantly. Otherwise, get some good soil and water once or twice a week. Either will work fine. I actually prefer soil.
