Hi, Can anyone tell me what could this be? Only on...

dou_cali_an, I dimmed the lamps to 25%(150w) and the top leafs that were almost yellow at the top started to get green again, then i put back to 300w and the yellowing started to show... my lights are 80/90 cm away from the plants which i find very hard to stress them but this are very powerful lights, what i think is when i put it to 300w the light stress might be worst cause of some blockage or deficiency in the plant... my tap water is an ec of 0.3 i might need to add some calmag to 0.4/0.5 ... could be calmag problem... as DrRaccon mentioned.

I will give you a simpler solution to identify a deficiency or an excess. Always look at the plants out of the light because the spectrum does not allow a correct diagnosis and can be misleading. Do you drain? To know if your plant is deficient or excessive, just look at the lower leaves, if they are intense green and the top is yellow, it is an induced deficiency caused by an excess. Another small element is the edge of the leaves, if it is yellow it is also a sign of excess. It is very rare to have a deficiency if you follow the feeding chart and use tap water, it is more often an excess due to a nutrient blockage. Concerning the small yellowing it is nothing serious, it can be genetic. The vein is indicative but at this stage it is not much...

DrRaccon, The Ec of the water before nutrients is 0.3 which i believe is around 150-200 ppms, So possibly could be a cal mag deficiency. The tips of the leaves are starting to be very light green/yellow.

Hi Nor_Cal_Kannabis, I dont think its a mutation. The tips of the leaves are starting to be very light green.

That actually looks like a slight genetic mutation on the leaf. Can happen where the plant leaf will split colors right down the middle. You can search around and find more info on it. It doesn't look burned at all. 🤘😤