Chaos Theory
I joined just to respond to these pictures...I have the exact same system with the exact same problem. I would post a pic but they would look just like yours! I switched to DWC for THIS show as I do not like washing all the rock in the 'bucket with rocks' system. However my yields have been all over the map with the DWC(Crop#1. 2.2#/1000, Crop#2. 0.6#/1000, Crop#3. 0.5#/1000, Crop#4. 1.1#/1000) and Im ready to go back to buckets but I hate giving up something I know can work (damn that first crop!!).
DWC
Grower XP: Deep Water Culture novice (0.5-2.2# per 1000)
3 gal buckets with Hydroton pro (typ: 2.7# per 1000)
Dirt (I hate dirt!) moderate (1.2-1.8# per 1000)
Strain: OG Kush / Purple Kush
Lights: 500W start ramps up to 1000W by week 3
Water Temp: 66-69F
Room Temp Day: 90F (ranges from 88-92)
CO2: 1000 ppm (from tank, not burner)
Room Temp Nite: 78F
Humidity: 60-75%
pH: 5.9-6.5 (fluctuates)
Nutes: Nutrilife Powder A/B/C (@1000ppm)
Nute Adds:
Superthrive, SM90
Water Source: Well (untreated, 300ppm from well alone)
Reservoir Change: Every 5-7 days
Redox: xxx mV (no meter yet)
I have run a few crops through now and can always start well with nice roots, leaves etc but within three weeks of veg ONLY SOME of the plants (~25%) start to show the signs you presented, others are 90% healthy (I only say 90% because I know how they should look!).
Points to note:
1. All Roots (affected and unaffected) start very well but within the three weeks some browning starts to show. New root shoots are present on healthier plants.
2. Affected plants and unaffected plants share same reservoir.
3. ***All plants always appear to be under a little bit of stress on stems. ALL new growth always seems perfect but shortly thereafter the stem starts to show moderate amounts of red. All leaves look like they're stressed a little bit as the leaf stem (petiole) goes red very soon after emerging (again, the new growth is perfect!). Yes, an unhealthy plant will put resources to the new growth centers at the expense of the rest of the plant. It appears the stress gets worse as I up the lumens (digital ballasts 50/75/100)...but only some!
4. Room has very little exhaust as the AC keep the temp and humidity in control (separate humidifiers and dehumidifiers also).
5. Leaves of affected plants appear dark green with deep veins and lower plant leaves will begin to yellow and die. The affected plant will finish very early with horrible yield.
6. Leaves of affected plan shows downward curl on ends.
7. Roots of affected plants are sub par. Brown with what appears to be some root rot. Why aren't all plants affected??? I am currently researching REDOX potential and looking at an ozone treatment system to eliminate any possible bacteria (Pythium?) coming from the well.
8. My other room has the exact same issue however there are two plants of a different strain (i'm told they are sugarshack, aka pinebud) that show NO sign of stress at all where others are affected as above (ie some healthy (8 on a 10 scale) and some not (2 on a 10 scale), pine bub (10/10).
Its the quasi-randomness of the affected plants that has me stumped. I know I'm missing something but I'm at my rope's end and my knot isn't holding!!! Any feedback is much appreciated! : )