DWC - four weeks in - Looks like Mag deficiency maybe?

[JohnC]

Hi folks,

My four-week old Berry Bomb has developed some kind of deficiency that has appeared two days after topping her.

It looks like it could be a magnesium deficiency but I'm not sure.

Here are some particulars:

• Strain: Berry Bomb (Indica-dominant hybrid, feminized seed from Bomb Seeds)
• Medium: Hydroton in net pot; 10-gallon reservoir with 5 gallons water.
• Light: G8LED 240-watt full-spectrum LED; suspended 20 inches above net pot
• Light schedule: 18 hours on / 6 hours off.
• Nutrients: GH Flora Trio (FloraMicro, FloraGro, FloraBloom), also using CalMag and HydroGuard.
• Ambient Temps / Humidity: Temps are consistently at 70-75 degrees during the day and mid-60's at night. Humidity currently hovers around 38%
• Water Temps: During lights off, water temps drop to about 66 - 67 degrees. During lights on, the water temp will stabilize at 69-70 degrees.
• Water PH: At the beginning of this week, water PH was at 5.8. Today, water PH is sitting at 6.0.
• Nutrient levels are per "Week 4 - Mid Growth" at 2/3 strength from the attached journal.

Does the leaf discoloration look like a magnesium deficiency or would you learned folks suspect something else? Nutrient burn perhaps? Please help.

[alltatup]

Hi John, everything sounds good. Why don't you try a 24 hour flush just in case there is nute lockout from too much salt buildup. I had that happen on my previous grow, and as soon as I flushed them, they bounced right back.

[Burny]

The affected areas i see on your leaves look like where nutrient solution has gotten on them. Are they getting wet? Is the black stuff staying damp?

[JohnC]

alltatup - My plans are to do a reservoir change today. I'll recalibrate my meter prior to the change to make sure everything is dialed in correctly and I'll PH my nutrient water to 6.0. Then, as the PH slowly drifts up this week, hopefully the plant will be able to absorb the magnesium I think it needs.

Burny - The black material is just neoprene that sits on top of the reservoir as a light blocker. It is not getting wet or damp at all. I'm pretty careful when replenishing my reservoir and there is no spillage so the plants are not getting wet or splashed on.