Yellow leaves - 4 week flowering

Thread starter #1
Hello growers,

Id like to ask you for help with my "office grow". Form first:

What Strain is it? White Siberian (WW x AK47) x Northern Lights
Is it Indica, Sativa or Hybrid? What percentages? Dunno
How Many Plants? One lady
Is it in Vegetative or Flowering Stage? Flower
If in Flowering Stage... How Long? 28 days
Indoor or Outdoor? IN
Soil or Hydro? HYDRO
If Hydro, Reservoir size? 8 litres of water
If Hydro, Reservoir Temperature? 22 celsius
If Hydro, what type of Medium? Hydroton
If Hydro, what type of Setup? DWC with dual 3.6W air pump (2 stones)
Size (Wattage) of Light? How Many? 1x 150W HPS
Is it Air Cooled? NO
Temperature of Room/Cabinet? 25 Celsius
RH of Room/Cabinet? 40%
PH of Medium or Reservoir? 5 - 7
Any Pests? NO
How Often are you Watering? Full dosage, then pure water to maintain level, once a week complete change with full dosage
Type and Strength of Fertilizers used? Advanced Hydroponics - full dosage, for phase 1 of 2 flowering
Size or Square Footage of Room? 0,6 x 0,6 metres
Roots Nice white healthy

Since the reservoir is that small I have been struggling maintaining proper PH but check it 2 or 3 times a day to lower to 5.5 - 6. Lower leaves are yellowing too but I consider this a normal thing.

150W is not that hot so despite some buds are quite close due to limited size of my box I don't suspect this is the main cause since there are yellow leaves even farther from light.

I also switch OFF air circulation overnight, could it be the problem that due to small size of the box, the plant is actually choking? :icon_roll

My thougts:
  • Nitrogen deficiency due to pH or improper feeding due to small reservoir
  • Light too close
  • Plant is choking due to air switched off overnight

Thanks for you help

Here are some pics for you (can be seen well on P1090757.jpg)
 
Thread starter #3
Are you supplementing with any Mag-Sulfur and Silica?
no other supplements, just AH dutch formula Grow, Bloom + Micro 1: 2: 1

I used to grow in large DWCs long time ago .. I see the size of bucket really matters .. quite difficult to provide optimal feeding

Do you think that those leafs can recover to normal when they get what they need?
 
Looks like N (or not enough light) and Mg deficiency to me and since you're about a month in I'd think Mag-Sulfur would be good to try and Silica might help with N uptake if, in fact, it is an N deficiency.