Hi, you can also check this by measuring the EC value of the runoff, which should be between 1 and 1.6. If it's lower, you have no nutrients or just a little. You can buy one at the hardware store; they're often cheaper than those from the grow shop and do exactly the same thing. I get mine at Toom from the reí compo. Look for one suitable for flowering, for example, there's the NPK kit value of 3.5-6-6 or something in that range. And then start slowly with the dosage. I also water according to the EC value, since tap water already has a base EC value, you can't always go by the manufacturer's specifications. Plus, with organic nutrients, it takes a bit longer for them to kick in since they first have to be processed in the soil by microorganisms. With mineral nutrients, it goes faster, and after a few days, they're back to being top-notch. Hope this helps you a bit, feel free to reach out if you have any questions.