Strange pigmentation that looks like a phosphorus deficiency

Hello people
I’m growing five White Widow plants and one plant of unknown origin (derived from a regular, non feminized seed, the exact origin I can’t remember but I guess it is one of those rodelization seeds or perhaps a seed derived from a pollinated flower of some plant I was growing outdoors). I call it a bastard plant. This one suddenly started to show a pigmentation on the leaves, that has turned some leaves purplish brown:



I think you can see around the bastard the White Widows, they look very healthy and beatiful and have all the life in those vibrant green leaves.

I initially thought of a phosphorus deficiency but it doesn’t seem the case because they’re on their 4th week flowering and a few days before I had started (only for weeks 4 and 5) using a boost fertilizer along with the usual bloom fertilizer.

I use the Flower Power brand of fertilizers and pH’d water at 6.5.
Light: DIY led lights 2 lamps at 3000K and 1 lamp at 5000K) more or less 200W real power from the socket and the grow box is 80 cm x 80 cm x 160 cm. Leds are 15-25 cm from the top of the tallest plants. This bastard plant is a sativa-like plant and it’s very long and thin, perhaps for this plants leds are a little closer.
No overfeeding, no overwatering, and I consider the environmental control is fairly good. In the night the temperature may be 10-15 ºC cooler than the temperature during the day (form 5 am to 5 pm the lights are on, temperature 20-25ºC and humidity 50-60%. In the night since we are almost in winter, temperature may drop to 5-10 ºC. Four fans keep on circulating air 24/7. I think the grow box environment is a little warm for the plants during a part of the day but cold in the other, but they’ll have to endure, I can’t provide them heating for the night. It is not freezing cold inside but I guess it may be a little cold for them to feel totally comfortable though.
What puzzles me is that the Whote Widow have received the exact same treatment as this plant and none of them is showing this coloration of the leaves.
Finally I’d like to say that the leaves don’t look sick, they are smoot, firm and fresh. There are some yellowing leaves but I’d say it’s normal to have some yellow leaves by 4th week flowering.
I’d appreciate your opinion if you have any.
Greetings from Uruguay and good bye!

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Looks like a Phosphorous deficiency to me. You may need to up the feeding of just this 1 plant. Each plant is different, and you cant treat them all the same.

Typically sativas tend to be from warm climates and really love the heat and intense light . It is simply changing colours due to the cold temps at night . The plant looks very healthy so I wouldnt worry too much. If you can raise the lights off temps a bit she will grow a bit faster. Some of the colours are amazing , dont be surprised if it turns black.

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I have researched the difference ways off getting some color into our plant’s and one way is to have the temperatures go up and then drop they feel healthy to you so I would definitely consider this as a possibility. :v:

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Also while using LEDs, your daytime temp should be in the low to mid 80s for optimal leaf surface temps. Nighttime temps should only deviate 5° or so.
The reason for this is because LEDs dont have adequate IR like HID lighting does.

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