Leaves undercurling with black patches

[JohnnyAutzen]

This outdoor Blue Magoo plant is 7-8 weeks old and has never been fertilized. I have it in a 25 gallon cloth grow bag with Fox Farm Ocean Forest soil. All of the plants in the garden are doing very well but this one recently started to get undercurled leaves with black spots. Any guess what this is and how I can fix it asap? Much appreciated, thank you!

 

[Pewterdude73]

I am no expert but since there have been no replies I will give my noob opinion. This looks like a phosphorus deficiency. I would check your PH. Ocean Forest is PH adjusted to between 6.3 and 6.8 but if your water is way out of wack you can swing out of that range. Hard to say why just one of the plants is doing this unless it is genetic or possibly something in your rootzone. Some strains are just more susceptible to problems. Are you using well water? City water? City water should be set out overnight and aerated if possible to gas off any chlorine. Water softeners can also introduce problems if you are on well water. Sorry I could not be of more help but just wanted to shoot some ideas your way that might have slipped your mind. Again I am fairly new to growing (4 seasons) so before you try and fix a phosphorus def I would get a second and a third opinion, but definitely would not hurt to check your pH, make sure there are no root problems like fungus gnats flying around and be sure to use quality water. Check the undersides of your leaves for spider mites also as I saw some white speckling on one of the pics. (might be water droplet reflection/refraction). Hope everything works out for you because Blue Magoo sounds like a winner.