The more nutrients you add the higher the PPM. You take the reading of your nute mix and subtract the 60 PPM of the tap water to get the PPM of the nutes you're feeding.
Based on the color of your leaves making them look hungry, I would keep upping the feed toward that 900 end and see how they respond. The general rule is when the tips burn, back it off to the previous strength.
Based on the color of your leaves making them look hungry, I would keep upping the feed toward that 900 end and see how they respond. The general rule is when the tips burn, back it off to the previous strength.