Hello fellow growers,

I need your advice regarding the deficiency symptoms of my plant. The leaf issues started appearing around the beginning of the flowering phase (week 5–6). Suddenly, the leaves began turning yellow with some brown spots and reddish stems (see pictures).

At first, I tried correcting the issue with pH adjustments and Epsom salt since I suspected a magnesium deficiency (based on research, image comparison, and AI analysis). 
Then I switched to CalMag (Advanced Nutrients OG Organics Sensi Cal-Mag Xtra, which has a low calcium content), and most recently, I applied dolomite lime as a top dressing.
My goal was actually to keep things simple and just use plain tap water — no pH adjustments or constant mixing. 🙄

Do you think it’s really a magnesium/CalMag deficiency? 
Should I continue using Epsom salt alongside the dolomite lime? 
Could it be another deficiency, or should I add more nutrients? (I still have a mineral Hannalin line from Manna available as a fast acting alternative.)
Did I overdose with the dolomite lime? (First i thought it was granulated, but it was just compressed power set the fell apart by contact with water...)


Here are the details:

Strain: 1x RQS - Purple Punch Auto (free seed) in a 40x40 cm tent

Growth/flowering duration: 61 days old in total, flowering for 30 days

Soil: 5L Compo Bio universal soil with 5 weeks of organic pre-fertilization, 2–3 cm clay pebbles drainage layer at the bottom

Fertilization: Greenhouse powder Feeding — 10g BioGrow after 3 weeks and 10g BioBloom after 5 weeks as top dressing; one week ago, 40g dolomite lime (60% Ca, 30% Mg) as a top dressing. Watered every two weeks with BioEnhancer.

Water: Hard tap water with high calcium content (107 mg/L Ca), magnesium at 11.7 mg/L, and pH 7.4, which should be buffered by the soil (see last picture for water values [in german]).

Lighting: 100W, dimmed to about 30%, distance ~20 cm, DLI around 40 under a 20/4 light cycle (according to the Photone app).

Temperature 23°C, humidity 30–40%.

Watering: Recently 1.5–1.8L every 2–3 days, previously with longer intervals.

pH and EC: Tap water pH 7.4; sometimes adjusted to pH 6.2 with phosphoric acid before adding dolomite lime.

Thanks a lot for your input!

CalMag / Magnesium or another deficiency?