This is the auto right?
Your feed is very low. But I wouldn't bother putting it up now as you are coming into the harvest window in the next 10 days or so.
As for the multicoloured leaf, if your ph doesn't differ much from your feed from your water feeds (ph swings)
Its a bit hard to tell. But it looks like powdery mildew. Now I can't be sure on that. Does it wipe off? If so increase your air flow, poor ventilation?