There are many threads on watering schedules. I've read 15 min of flood 5 times a day with Ebb&flow. NONE at night.
Most hydro people will tell you to place some sort of circulation device in the tank, like air stones with a pump, or a power head(like one for a fish tank). This will circulate water in the tank. Thus oxygenating it.
I'm a reef tank person, and have studied that for many years. Most oxygen in the water is picked up NOT from bubbles (not much in a bubble), but from agitating surface contact with the air (lots of dissolved oxygen, water, air contact). An air stone pumping out bubbles moves a lot of water around, thus causing surface agitation. :thumbsup:
So if you don't have any circulation. Your tank can get oxygen deficient.
Also, you say the "stick" says 10. Most people test the nutes through PPM, or EC. Since none of us have a clue what "10" means. It'd likely help to break down the range. Is 10 low, med or high on the chart. Does it break down any of the individual NPK ratios? If not, what do the bottles say are the NPK ratios?
Here's a nice page I saved for plant issues, it doesn't show anything like yours. However it also doesn't talk about roasting your roots, or low oxygen CAUSED by roasting your roots.
Marijuana Plant Abuse
Still could come in handy for you on any other issue you see. :thumbsup: