Why are the lower, older leaves on my hydroponic plant turning yellow?

This is usually nitrogen deficiency. Nitrogen is mobile in the plant, so it gets pulled from older leaves toward new growth first when the reservoir runs light. Check your EC/PPM against the target for your crop and growth stage, and confirm you haven't been topping off with plain water only.

Why are the new leaves yellowing while the veins stay green?

That pattern (interveinal chlorosis) points to iron deficiency, and it's almost always a pH problem rather than a lack of iron in the mix. Iron locks out above roughly pH 6.5. Test and correct pH into the 5.5-6.5 range and recheck in 24-48 hours.

What causes brown, slimy roots in DWC or hydroponics?

Root rot, most often Pythium, thrives in warm, low-oxygen, stagnant reservoir water. Trim affected roots with clean shears, boost aeration, keep the reservoir under about 72F/22C, and sanitize the system between crops.

Why do my leaf tips look brown and crispy?

That's typically nutrient burn from an EC that's too concentrated for the crop stage, or salt buildup after evaporation without top-offs. Dilute the reservoir toward your target EC and resume feeding at a lower strength.

What's the white powdery coating on my leaves?

Powdery mildew, driven by high humidity, still air and cool nights. Improve airflow and circulation, reduce humidity, remove affected leaves, and treat with an appropriate fungicide if it's spreading.

Why did all my plants suddenly wilt at once?

In NFT and aeroponic systems especially, this is almost always a pump or power failure -- roots have little to no reservoir to fall back on and can dry out within an hour. Check the pump, power and timer immediately, and consider a float switch alarm or battery backup going forward.

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