How to Troubleshoot a Plant Problem Before Changing Nutrients

Before you change the feed, get the numbers: feed EC and pH, and the EC and pH of the last 10% of runoff after a normal feed. Add canopy air temperature, RH and a leaf temperature, and make sure every pot is actually getting its water. Root zone, watering and environment problems can all look like a nutrient problem in a photo, so measure before you touch the recipe.

What to collect first

• The mix: products, stage, grams per gallon and the real gallons in the tank. Weigh the powder and check the tank volume; a tank that holds more than you think reads low.
• Feed EC and pH at the outlet. If you read ppm, tell us the scale (500 or 700), or just switch the meter to EC.
• Runoff EC and pH: the last 10% from a normal feed, caught fresh in a clean container. Here's how we test runoff.
• The environment: air temperature and RH at the canopy, an IR leaf temperature, and a canopy PPFD reading if it started after a light change.
• Delivery: does the sick plant get the same volume as a healthy one nearby, and does its pot drain?

Check your meters first. Calibrate the pH probe in fresh solution and check the EC meter in a reference solution. In DWC or a bottom-fed system, send reservoir and system readings instead of runoff.

What normal looks like

At chart strength in RO water, the feed reads about 2.2 EC or a bit higher; tap water reads higher. We give about 25% runoff in coco and peat, and in coco we let pots dry back about 50–60% between feeds: light, never bone dry.

Match the fix to the readings

• Runoff pH low from buildup: do a pH-6.4 tap-water flush; the full steps are in Why Is Runoff pH Lower Than Feed pH?
• Runoff pH high: confirm your dosing first. If it really is underfeeding, raise the complete A+B mix in steps and allow a bit more dryback, then ease back as pH corrects. That isn't the fix for fresh rockwool or high runoff EC. More in Why Is Your Runoff pH Rising?
• Feed is below chart: bring it up to chart strength instead of cutting it further.
• One plant is off: do a timed catch from its emitter, then clean or replace the outlet. See why one plant looks sick.
• Pot stays wet and the plant droops: check drainage and roots before you water again. See drooping in wet coco.
• It started after a light or climate change: measure canopy light and leaf temperature and recheck VPD in our VPD calculator. Then work through what to check after a light change.

What not to change

• Don't add Cal-Mag, silica or boosters. Veg and Bloom already carry multiple calcium sources. See why you don't need them.
• Don't change one part. A and B stay paired. To change strength, move both together.
• Don't push EC until you see burn. No tip burn doesn't mean more feed will help.
• Don't feed your way out of a light problem. More nutrients won't make up for weak light.

Confirm the fix

Change one thing, then measure the same way you did before. After a flush, wait two normal feeds before you read runoff again. Judge by the new growth and steady readings; damaged leaves won't turn green again. Stuck? Send us the readings above and a photo.