Curious

[QuixoticQuipper]

2 x 00 seeds white widow auto's week 4 in 17 litre pots with Easy as organics water only living soil with easy as organics amendments and teas. Blumat automatic plant watering system. 90x50x160 growlush tent. VIPARSPECTRA Newest Pro Series P1500 LED.
4" INLINE FAN/CARBON FILTER. 2x6" oscillating fans.
Anyone familiar with this colouring of leaves? I'm fairly certain that it's not a pH or nutrient problem as only the much larger plant's leaves have these different colour shades. Stretch marks possibly? Genetics? She grew very quickly compared to her sister. Thanks in advance for any input.
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UPDATE
I have determined the cause of the issue. When growing with water only living soil you need to use a minimum of 50 litres of living soil to obtain the correct amount of available nutrients for the grow cycle.

[azorahai]

Looks like early stages of magnesium deficiency. I've never grown on living soil with organic fertilizers, so I'll let others chime in first, but you could try adding some epsom salt (magnesium sulfate) next time you water them, about 100-200mg/L should do the trick.

[QuixoticQuipper]

I shall investigate your hypothesis.
Thank you azorahai, much appreciated.

[SoOrbudgal]

.under fed sorry i'm in the USA don't use metric nor liter just seeing the plant colorings. That one did'nt get the same amount of N within that container.

[MeEasy]

By any chance is that plant closer to the fan? Looks to me like a slight case of wind burn