Problems with plants, magnesium/calcium deficiency?

From a fellow grower:

I have soms problems with bij plants.
The leaves are turning brown with brown spots.
Please see the pictures attached.
It looks like magnesium/calcium deficiency?

It is probably a pH problem, maybe a nutrient salt build up.

Happy growing,



I’m from Holland.
It regards 3 Autoflower Easy Rider and 1 Autoflower AK47
Planted the steeds 6 weeks ago.
They starten flowering after 2,5 weeks.

Growing on soil; 11 liter POTS
250W lamp and Lucilu Small Reflector.
It regards a Bonzana 250 growing box.
Winflex 185m3/h and Prima Klimaat filter 2600-mini; 240m3.

The growing box (made of mdf) is 60*60cm and 176cm heigh.
It is dificult to control the temperature in this box.
Tomorow they are flowering 4 weeks. Problemen with the Brown leaves is getting worse. PH unknown. Never knew that I should check the pH of soil…

Plants get 20h light and 4h dark.

Feed them with Bionova Soil Supermix and with flowering Bionova PK 13-14
Just for sure I bought Ca and Mg.

Do you need more info?
How do I measure the pH of soil? The strange thing is that the AK47 is having most problems. The other 3 less (Easy Rider).

Best regards.


Yes, pH can cause nutrients to become more or less available to the plants. In extremes they can become entirely unavailable (lockout) or they can even become more absorb-able to the point of being toxic (nute burn).

Also nutrients can build up in the soil themselves. And this can be tested for or measured as well with an EC or TDS meter.

Here is a blog on our site about testing the soil.

Happy growing,


Hello MacG,

Just ordered a PH meter for soil.
Thank you for your quick reply.

Best regards,


Ser1976 said:

I measured the pH of the water I give the plant, just tapwater. Th pH is between 7-7,5

Since I know that I gave the plants SPA Reine water out of bottles. This water has a pH of 6. Same time I ordered ph- Bloomington and now I lowet the pH of my water before feeding the plants.

I also bought a soil pH meter. PH of the soil is stille 6,5-7

It juist from last weekend I starten with the bottled water and flowering pH of tap water. I assume it takes some time to restore the values of the soil?

I trad that the pH of the water should be between 5,8-6 for soil?

The soil pH meter is nog so accurate and the water I measured with pH paper. I try to regulate it at pH 6.

For this week I stopped giving the p!ants nutrients.
I will start next week again. Next Monday it’s week 5 of Blooming. I expect to finish in week 50.

Thank you for your advise.

Best regards.


I’m not sure what you are doing or how you measured. Maybe a bunch of typos?

Soil pH should be 6.5.

6.5 should be going in the top of the soil, and about the same number, or very slightly lower should be coming out the bottom, as a point of reference.

I’m glad things do seem to be getting better.

Happy growing,