Weird little brown spots on leaves

[GuerrillaWarf]

Hello,

Once again I'll need your expertise to save my plants.

My growing situation:
I'm growing to plants in a closet, they've been in the vegetative stage for about 6 weeks and recently I've changed the bulb and the light/dark cycle to 12/12. The strain is Afghan Skunk. I've been feeding them with ATAMI Grow-C (and Bloom-C after the light cycle changed).
Everything is going fine so far, and the information in this forum has been more than sufficient for me to get the experience I'm lacking. However one of the plants is showing brown spots on the leaves, high and low. For what I've been reading it would probably be a fungus infection or pH problems or phosphorous deficiency. It's strange that only one of the plants as them, that would eliminate the last two possibilities. I've measured the pH level sometimes and seems to be between 6-7.
Some photos:

I thank you in advance for your help. Regards.

 

[The843Badfish]

I think this is going to be a magnesium deficiency? My Afghani kush did the same thing towards the bloom phase.

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[jhfhklsnhfldk]

Yeah, looks like you may have the first signs of calcium def which leads directly to mag def. Do you feed molasses or cal mag? In soil, I have had better luck with molasses.

 

[GuerrillaWarf]

Thank you for your quick replies. You guys are the best . It makes sense that it might be some mineral deficiency, the water in my region is know for not having a lot of minerals. I don't have the experience (yet) to recognize the symptoms.

Do you feed molasses or cal mag? In soil, I have had better luck with molasses.

I don't feed either. I've been reading a little bit about it and I think I'm going to try to use use molasses and see how it responds to it. If I don't see improvements this week i'll try cal mag.

I'll post the results. Thank you again

 

[Cultivator]

its def calcium deficiency, add calmag. keep ph at 6.4 for feeds.

 

[GuerrillaWarf]

Hi again,

So I've been adding molasses with the other nutrients for a week now and it definitely made the difference, the plants look a lot better and the one affected by the brown spots seems to be healthier. The spots didn't go away but the leaves didn't get any worse. I suspect that the affected leaves wont heal but as long as they stay as they are the plant will continue to do well.

Thank you again for all your help

 

[AngryBird]

Glad you solved it and thx for reporting in the good news