Oh wow, those are some yellow plants! I have to agree with some of the others here, it's DEFINTIELY a pH problem... you actually have 2 separate issues going on. Let me explain.
1) Different medias need different pH levels for proper nutrient uptake, which is based upon the amount of organic matter. Decomposition of organic matter will lead to the production of organic acids, thus lowering pH. This is why the pH range for soil is up around 6.5-6.8, whereas hydroponics, with no organic matter, has a pH range of 5.5.
So running a mostly organic grow means you should keep your pH in the high 6s.
What's important to understand is that pH is reported in logarithmic units. That means each whole number represents a 10-fold change in the acidity/basicness of the water. Water with a pH of 5.5 is ten times more acidic than water having a pH of 6.5.
AND THEN...
2) There's the fact that you're using RO and distilled water, neither of which have carbonites and bicarbonates. These contribute to the alkalinity of your water and buffer against pH changes. So without these, your low pH is having an even more dramatic effect on your plants!
So i would switch to regular water, if possible, making sure it's just below 7. It's hard to make a call about your nutrient levels, as so much of them are probably locked out and unavailable to the plant right now, 1/4 strength is low. If they don't start darkening up a few days after adjusting your water problems, i would definitely up your amounts.
Good luck! :)