first, you need to clear up those roots ... a good flushing with hydrogen peroxide added, usually does the trick, quickly ... I have never seen a recommended dosage, but my usual '2 ounces per gallon' has worked well for me, in the past ... it will also kill beneficial bacteria, which will need to be replaced (Fox Farm Big Bloom, etc) ... I think my deep green/leathery leaves are due to excess humidity, but I'm not positive of that ... over-nitrogen will burn the tips of the leaves first, I don't think that's your situation ... :smokin: