Hey everyone,
This is my very first cannabis grow and I’m already feeling a bit lost with my 4 seedlings (regular seeds). They’re 12 days from sprout and I’m trying to figure out if I’m dealing with:
• Salt buildup
• Overwatering recovery
• Light stress aftermath
• Calcium deficiency
• Or just normal seedling weirdness
Any help or extra eyes on this would be hugely appreciated.
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Setup & Gear
Tent:
Small 2x2 mother/seedling tent
Temps get warm (~84°F lights on)
AC Infinity Cloudline T4 exhaust + oscillating fan
LED driver moved outside the tent
Light:
Mars Hydro TS1000
Originally too close (~5 days ago)
Now 30 inches above canopy
24/0 light schedule
Medium:
Fox Farm 70/30 pre-buffered coco coir
(I also buffered it myself)
Containers: 16oz red Solo cups
5 drainage holes each
Elevated on rack for full drainage
Water:
RO water (~10–47 µS EC baseline)
Nutrients:
Jacks 3-2-1
• 5-12-26
• Calcium Nitrate 15-0-0
• Epsom Salt
Additives:
GH Rapid Start (1–2 ml/gal)
GH Armor Si (1–2 ml/gal)
GH CaliMagic (0.5–1 ml/gal recently)
Great White Mycorrhizae (¼ tsp/gal)
pH: 5.8 – 6.0 target
(mix drifts to ~6.2 after a few days)
Starting EC: ~505 µS
Environment:
Temp: 72–84°F
RH: 70–82%
VPD: 0.7–0.8 kPa
Genetics:
Mr. Nice Seeds – Critical Mass (regular photoperiod)
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Timeline & What I’ve Done
Days 1–7
Very light watering using spray bottle
20–60 ml per day around stem
Coco kept evenly moist
EC: ~500–550 µS
pH: 5.8
Days 7–10
Noticed:
• Slight yellowing
• Brown tips/edges on fan leaves
• Some drooping
• Extremely compact nodes (almost no spacing)
• Slow upward growth
Day 8
Suspected light was too close → raised to 30 inches.
Day 8–11
Stopped watering/feeding for 3 days to dry coco.
Cups previously felt heavy and I suspected overwatering.
Also noticed green algae forming on top of the coco, so I lightly covered it with fresh coco.
Day 12 (Today)
First runoff test after feeding 200 ml:
Input solution:
740 EC Jacks 3-2-1 mix
+ CalMag 1 ml/gal
+ Silica
+ Rapid Start
+ Mycorrhizae
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Runoff Readings
Cup 1: 1300 µS / pH 5.6
Cup 2: 1025 µS / pH 5.9
Cup 3: 1170 µS / pH 5.8
Cup 4: 1410 µS / pH 5.5
Runoff drift: +275 to +660 EC
This suggested clear salt buildup.
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Large Flush Performed
After seeing the runoff numbers I did a much heavier flush.
Each cup received:
1 liter of nutrient solution
740 EC Jacks 3-2-1 mix
+ CalMag 1 ml/gal
+ Silica
+ Rapid Start
+ Mycorrhizae
Allowed full drainage through bottom holes.
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Current Plant Status
• New top growth looks healthy and green
• Lower fan leaves have yellowing + brown tips/spots
• Likely old damage from earlier light stress or possible Ca issue
• Leaves still slightly droopy (but improving after dry out)
• Nodes extremely compact (almost no internode spacing)
• Above-ground growth feels slow/stunted
Roots may be catching up though.
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Questions / What I Need Help With
1. Did the 1 liter flush at 740 EC likely remove enough salts, or should I flush again with:
• Lower EC (400–500)?
• Plain pH’d RO?
2. How soon should I feed again after such a big flush?
• When the top of the coco dries?
• What EC should I restart at?
3. Is very compact node spacing + slow vertical growth normal for day 12 seedlings in coco solos?
4. Are the brown/yellow tips likely:
• Old light stress damage
• Or ongoing Ca/Mg issue?
5. Should I keep Cal-Mag in every feeding with RO water?
6. Am I missing anything obvious with my environment?
Ventilation: AC Infinity T4 + oscillating fan
RH: 70–82%
Temps: 72–84°F
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I’m documenting everything with photos every few days, but as a first-time grower it’s hard to tell whether they’re just slow or actually in trouble.
Any advice, similar experiences, or “wait a few days and they’ll explode” stories would definitely help calm my nerves.
Thanks in advance
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