Help identify marks on leaves, stunt grow

[clash]

Hi,
I am growing second time in 2x2 tent. Having issues with slowed growing rate, and few flowers with little amount of pistles.
Days from germination: 45.
Strain: Auto Northern Light.
Light: 18/6. vipar xs1500 pro 50% dim.
Medium: 70% soil 30 % coco.
Water PH: In 6.0, runout around 7.5.
Trainig: LST.
Feeding: First 10 days watered with filtered RO water, no nutrients. After that started giving 25% of Tripart HW nutrients according to charts but with tap water with 200-300 PPM.

After the last feeding with full "preflower" dosage of Tripart HW but with 1L RO water, next day appeared light brown marks on foliage. Could it be cal mag deficeny or something else? Help these girls to have a nice harvest

 

[Creeperpark]

Hi,
I am growing second time in 2x2 tent. Having issues with slowed growing rate, and few flowers with little amount of pistles.
Days from germination: 45.
Strain: Auto Northern Light.
Light: 18/6. vipar xs1500 pro 50% dim.
Medium: 70% soil 30 % coco.
Water PH: In 6.0, runout around 7.5.
Trainig: LST.
Feeding: First 10 days watered with filtered RO water, no nutrients. After that started giving 25% of Tripart HW nutrients according to charts but with tap water with 200-300 PPM.

After the last feeding with full "preflower" dosage of Tripart HW but with 1L RO water, next day appeared light brown marks on foliage. Could it be cal mag deficeny or something else? Help these girls to have a nice harvest

You are doing good and have a good start friend. Thanks for posting. If you use RO water you need to buffer it with cal mag or your pH will drop very low in the substrate. It's best to maintain a steady EC from the beginning with every watering. Use a low ppm of fertilizer with RO water buffered with cal mag. If you stop and start nutrient EC or change the waters the plant will be stressed and may crash. Your problem here is you flip-flopped from feed to no feed and water changes during the grow. Maintain a steady EC and pH from the start by doing the same thing throughout the whole grow.

 

[DARKSIDER]

Hi,
I am growing second time in 2x2 tent. Having issues with slowed growing rate, and few flowers with little amount of pistles.
Days from germination: 45.
Strain: Auto Northern Light.
Light: 18/6. vipar xs1500 pro 50% dim.
Medium: 70% soil 30 % coco.
Water PH: In 6.0, runout around 7.5.
Trainig: LST.
Feeding: First 10 days watered with filtered RO water, no nutrients. After that started giving 25% of Tripart HW nutrients according to charts but with tap water with 200-300 PPM.

After the last feeding with full "preflower" dosage of Tripart HW but with 1L RO water, next day appeared light brown marks on foliage. Could it be cal mag deficeny or something else? Help these girls to have a nice harvest

Whats your temperature in tent maybes needs raising ..

 

[clash]

You are doing good and have a good start friend. Thanks for posting. If you use RO water you need to buffer it with cal mag or your pH will drop very low in the substrate. It's best to maintain a steady EC from the beginning with every watering. Use a low ppm of fertilizer with RO water buffered with cal mag. If you stop and start nutrient EC or change the waters the plant will be stressed and may crash. Your problem here is you flip-flopped from feed to no feed and water changes during the grow. Maintain a steady EC and pH from the start by doing the same thing throughout the whole grow.

Appreciete your attentation for my issue. Will follow your advices. I am planning to add TA CalMag supplement (2ml/l) for my RO water. Coco in my substrate is only an addtion, so I am not sure how to treat it and I am afraid to overfeed. Is it good watering schema: feed, water (RO with CalMag), feed, water...? What these marks on leaves are sign of, deficiency, toxicity or just not stable watering solution stress overall? Today the leaf from the first photo dried and curled upside even more, stem became weak, light to flex. Thanks in advance!

Whats your temperature in tent maybes needs raising ..

That's true. First 40 days daytime average temp was 21-22 C. Now is around 25-26 C, hope this will be more stable till harvest.