Fan leaves yellowing/dying off ; Help with Nutrients

Been trying to research and learn things on my own, but this issue seems to be getting lot worse. I think I have a nutrient deficiency but don’t want to overfeed so looking for advise from you all since this is my first ever grow. It started slowly about 3 weeks ago and has progressively gotten worse working it’s way up the plant on the fan leaves.

All ticket info below…65 days from sprout and about 4 weeks into flower (autoflower). It looks like Nitrogen deficiency but would that happen this late in flower? Maybe Potassium deficiency? The top leaves are also turning purple and my other Amnesia Auto is not. My PH has always been spot on.

Note, I’m using RO water and had previously been feeding 5ml of CalMag every watering so I’m going to cut that back (maybe its blocking out other nuts?). Been feeding plant 5ml of Tiger bloom starting about 3 weeks ago and feed about every other watering to try keeping PPM’s between 1,000 and 1,500. Should I add some Grow Big to up the Nitrogen? Or should I try like 7.5ml of tiger bloom which would be 3/4 of the recommended amount per the FF feeding chart?

Amnesia Haze Auto from IloveGM
Method: Fox Farm Ocean Forest Soil
Vessels: 5 Gallon fabric pot
PH of Reverse Osmosis water going in is 6.6/ Run off = 6.5 to 6.7
run off PPM/TDS = 767
Indoor = 4x4 grow tent in garage
Light system = 2 ES 300 LED’s at 100%
Temps; Day = 70F; Night = 65F
Humidity; Day = 53%, Night 45%
Ventilation system; 6" Cloudline exahust fan + 12" oscillating fan on wall
deHumidifier = set to 45%
Co2 = No

This is OLD PIC from 2/28 when problems first started.


im no expert but ph seems a little high. from what I know you want your water ph 6.2 to 6.5 is best. might be a nutrient lock out issue. my run off is normally 6.6 to 6.5 I personally try to ph my water at 6.2 like I said im no expert

A couple of things: first, don’t bother PH’ing straight R/O water as any reading you get will be ‘spurious’. Solids have to be present (50 ppm or more) before your meter can accurately read the liquid. Whenever it’s just water go ahead and dump it in.

Plants will extract all the goodies from early fan leaves and then drop them during flower right after transition. This starts at the bottom and works it’s way up. Just remove when the plant releases them. You can take all of those off. Some minor defoliation during flower is a good thing for airflow and light. About two weeks before harvest, depending on ambient conditions, you will start taking most of the leaves off in anticipation of harvest.

Fox Farms feeding schedule is based on U.K. or Canadian numbers or 700 scale. We in the USA are on a 500 scale (NACL scale) so if you use US meter to meet UK numbers you will be over-feeding. 900 to 1,050 ppm, NACL scale, is where you want to be. You don’t need any grow nutes now.

Temps are a bit low but workable. Just remember that lower temps means slower living processes. This is another reason to lower your feeding numbers.

Look up VPD for cannabis and you’ll have another tool for your grow. The chart is self explanatory.

1 Like

@Myfriendis410 thanks for the response and I’ve started to look into VPD as well as cutting off the old dying leaves.

hopefully it will improve over the next few days. I’m working on getting the temp/humidity per the VPD table for flowering I found.

They will release very easily from the stalk with a mild tug.