yellow leaves

Your runoff should tell you. It's a yellowing that climbs so it's probably a nute problem, but a root problem could cause it too I suppose. I assume you're feeding at an EC of 1 and a pH of 6.5. Test your runoff. If it's the same, it either means your plant isn't drinking (root problems) or it could mean that you have an absolutely perfect mix (unlikely I think, plants needs change constantly). If your EC in the runoff is really low, like 0.5, then you should probably feed more. This is usually accompanied by an increase in pH. Your plants are not getting enough nutrients. If the EC of the runoff is really high, you probably have hot soil and a nutrient lockout. The pH will probably be under 6 in this case. Once you figure out the problem, figure out how to attack it. For roots, some beneficial bacteria or an H2O2 treatment might fix it. If you need to increase your feed (my first guess), then all you have to do is increase your EC. If the EC of your runoff is really high, then you'll need to flush.