Still More Yellowing Leaves

Greetings, I am very new at this and have been reading the numerous threads to try and figure out my situation. This is a freshly built out room. Here is the situation:

The plants start great (out of veg) with great color. Within a week of bloom start, the leaves start fading from a rich green, to pale green, to yellow.

Aound week 3 some random leaves start getting gold tips and appear to be light burn or 03 damage (See enclosed Photots). These leaves are located around the middle of the plant.

We can't figure out why.

400 SQ FT Bloom room (12 dark/12 light)

Temperatures range from 70 - 80 degrees 24x7

1 - 1000 CFM fan running 24x7 exhausting air out

1 - 500 CFM fan running 24x7 sucking air in

2 25,000 BTU air conditioners on VENT keeping temperatures just right

Each tray are running 1000 watt hortilux. Lights are placed at least 24 inches away.

15 mintue watering times twice a day (15 minutes before lights on, 15 minutes 5 hours into the "daylight")

5 Pest Strips

Smooth Jazz playing in the back ground

I am using the Aquaflakes A+B and Multi-zen for weeks 1-3 and Bud XL for 4-8 (following the standard House and Garden recommended feeding regime).

We PH and EC every day and make sure it is nuts on.

We have 25 Gallon reservoirs using RO water (EC around 30 when we start out).

What am I missing?

We have an option to go to a CO2 enriched room. We tried that for 2 days and that DEFINITELY accellerated the yellowing factor.

When Using the CO2, we vent the room during the "dark hours" only and then enrich the room only during the light hours. We evacuate the room every 3 hours for 30 minutes when running the C02. For now, however, the CO2 is off and we are running a fully vented room

So I discoverd that the PH meter was off (despite me calibrating it every week).


Got a new on and right out of the box, the PH of the reservoirs was about 6.5. (other meter read 5.5). I removed some water from the rockwool and found the PH of the rockwool was 7.0+

Could this be a PH issue?

Just to make things more interesting, I have been flushing the plants on the 7th day with RO (non PHd, so they are being flushed with RO at PH 6.5). I gotta believe that can't be good (now realizing this).

If so, how about emptying the reservoirs. Fill with PH 5, RO water. No nutes, and leave them on their normal watering schedule for a day. Basically this would flush the salts and re-ph the rockwool to a more reasonable ph. I estimate it will end up around 6.0 if I do this.

Please let me know your thoughts

Another Update:

We increased airflow to the room.

Here are the latest pictures.

I am about to burn down the room.

I just don't get it.

Samurai Jim said:

Another Update:

We increased airflow to the room.

Here are the latest pictures.

I am about to burn down the room.

I just don't get it.

Click to expand...

NEW DATA JUST IN:
I removed water from one of the Grodan Slabs in my Sea of Green. The Ph of the water was at 7.0.

We conditioned it with Ph 5.0 water for 5 hours before use????? (The slabs did sit idle for a few days before we put plants on).

Any comments? Anybody at all?

Looks like the same thing that happend to my girls aabout 4 weeks into flowering on a 13 week flowering heavy sativa plant.. But for me it was the MG time release ferts mixing with my fox farm ferts and burning fan leaves off.

OGKush00 said:

Looks like the same thing that happend to my girls aabout 4 weeks into flowering on a 13 week flowering heavy sativa plant.. But for me it was the MG time release ferts mixing with my fox farm ferts and burning fan leaves off.

Click to expand...

here's what they looked like after i flushed them thoroughly.. was too late though. Nute burn is very traumatizing to plants during flowering. still got almost 4 oz's off 2 plants though

OGKush00 said:

here's what they looked like after i flushed them thoroughly.. was too late though. Nute burn is very traumatizing to plants during flowering. still got almost 4 oz's off 2 plants though

Click to expand...

this pic looks more like what you got going on.. one i was looking for before but just found ;p

Have you checked the Nitrogen? Seems like a nitrogen deficiency..I would check out this link https://www.rollitup.org/marijuana-plant-problems/157345-have-plant-problem-check-here.html

You are just flushing with plain tap water right?

Thanks for the relplies, we are flushing with RO water. The PH of that water is about 6.5.

Thanks for your reply. In our research you are now the 2nd one that has suggested a Nitrogen deficiency. I will be going to the hydro store today to see what we can purchase. Do you have any recommendations for a Nitrogen supplement?

I just talked with the Hydro store. They suspect over watering? We water 15 minutes right before lights on and then 15 minutes 5 hours into the "day." The rockwool is very damp all the way up. They suggested not watering for a few days then going only once a day for 15 minutes 1 hour after lights on. Anyone have any comments on that thought?