Help identifying plant issues

Light: QB 240W LM301H + Epistar 660NM @ 26" from canopy - Dimmer set to 80%
Tent : 2.3' x 2.3' x 5.3'
Ventilation: 2x 6" fans - below and above canopy
Exhaust: Hyperfan V2 6" + Carbon Air Filter
Intake: Passive
Temp/Humidity: Day 25-27c @ 50-55% RH / Night 18-20c @ 50-55% RH
Medium: Promix BX + 60-80% perlite + Dolomite lime (1tbsp / gal)
Water: Tap - 150PPM @ 19c - left out for 24hours
Containers: 3x 2gal - 1x 3gal
Stage of growth: 6 weeks, veg, 6" tall
Strain: Wedding Cake - Feminized
Nutrients: Botanicare Pure Blend Pro Grow (9ml/gal) + Liquid Karma(3ml/gal) + Cal-mag plus (3ml/gal)
Feeding: 950PPM every water until 15% runoff @ 6.3-6.4 pH - every 3-5 days
Runoff PPM & PH: I haven't measured runoff PPM or pH in a few weeks. Last check the runoff pH was @ 6.4
Pests: Fungal gnats treated with yellow sticky traps

Symptoms: Yellowing of leaves starting halfway up the plant and browning rust spots. Lower leaves are unaffected.
Suspected issues: pH fluctuations, cal-mag deficiency, light intensity

These girls are just over 6 weeks old. They were stunted early on as a result of improper watering/feeding, too much perlite (causing the roots to grow only near the bottom of the pot), and reusing soil that was void of any nutrients.
In the last 3 weeks they have been growing at a healthy rate. However, last feed I started to give them cal mag after noticing some rusty colored spots.

3 plants are in 2gal pots, 1 was recently transplanted to a 3 gal. I plan of transplanting the 3 plants to 3gal pots before next watering.

I uploaded a PDF of the sheet I use to track my feeding/watering, and general notes.

Any help is appreciated

950 is kinda high,dolomite lime probably not going to help feeding like you do so calmag is the next best.How do u collect runoff ,really should elevate over a tray or something not gonna be easy at 5 weeks of flower.Ph I think is right but the added lime may be messing with it.Too low will block Ca/Mg.Good time to try one plant at a higher pH.Plants look good otherwise.

When I measure runoff I simply put a container underneath a plant then I water the plant and measure the pH and PPM from the container. I added dolomite lime because I read that Promix may not have enough of it, and other recommend adding 1-2 tbsp per gallon of promix. Do you think the problem is the pH is too low? The dolomite should be slowly raising the pH, so I would have guessed the pH was too high.

Your feeding to runoff though so not sure the lime stays.Promix will be low before its high in pH.As said try higher on one,its how we learn.I mix my promix with gaia dry and dont pH, my tap water its 7.2 ish.

My pH from the tap is 7.3 - I'll give it a try, thanks!

phaz said:

My pH from the tap is 7.3 - I'll give it a try, thanks!

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Try 1 and see,wont hurt.