This Northern Lights Auto Flower is only 2 weeks old but the brown spots are getting worse. Looking for advice from others here as this is my first grow. My thought is that since I'm using RO water, it is a calcium and/or magnesium deficiency.
Soil is FF Ocean Forest and since it is only 2 weeks old and growth seems stunted, I have only been watering with spray bottle when top of medium dries out. I have three other Autoflowers (different strains) grown from the same bag of FFOF soil in my 4x4 tent that seem to be doing great without any CalMag.
Would you all suggest mixing say 2ml of CalMag in a 1/2 gallon of RO water (PH'd to 6.5) and feeding the plant?
I looked at the leaves (top & bottom) under 10x loop and didn't see any bugs. The first few brown spots were because I had water spots from watering and the light burned, but this is getting out of control now :)
----Temps have been consistently around 70F with humidity 70-75%, have 8" non oscillating fan on floor. Running 2 ES300 LED lights dimmed to 75% about 24" from plants running 18/6.

Just watered as you can see in pic below

Pic below was on DAY 5 when I got water on the leaves

Thought I would post an update on my Auto Northern Lights since its been 65 days since sprout and entering 4th week of flower. I chose not to defoliate or LST since this is my first grow and just want to get to harvest safely.
The spots got smaller but never went away. They seem to more prevalent on the upper leaves so thinking it is an immobile not a mobile nutrient. Or it is just a bad seed.
I welcome anyone's thoughts on how the plant is looking, if those spots are something I should be concerned about, etc. Run off PPM is 1,430 with PH of 6.6 (FFOF soil). Feeding 5ml of Calmag but going to reduce that. 1/2 dose (5ml) of Tiger Bloom every other watering.