First Signs of Something Wrong -- What? (Pix)

Hi all -- My newest growth is showing yellowed leaf tips, and I have one tiny necrotic (dead) spot on a fan leaf. So I think I am seeing the first signs of some problem, most likely a nutrient deficiency. The plants are in soil: 10 parts FFOF, 4 parts perlite, 1 part vermiculite; they were transplanted from 4" pots into 7 gallon cloth containers of this soil a little less than 3 weeks ago. As FFOF is rich, I haven't fertilized with anything yet.

Looking through "The Cannabis Encyclopedia" by Jorge Cervantes, my best guesses were Boron or Zinc deficiency, but he claims that boron deficiency is caused by "extremely poor soil," which I'm sure is not the case, and that zinc deficiency is caused by a pH above 7.0; I tested mine with a "rapitest" tester, using a sample about 3 inches below the surface, and it's 6.5 or slightly less.

They're under LED panels which I had at 22 inches above the plants; I raised them last night to 25 inches above, in case that was the problem. The LEDs include a couple of UVB diodes, and perhaps the necrotic spot could be due to a burn from the UV being too close -- maybe focused by a water droplet that got on the leaf during watering. Could the leaf tips be yellowing also from the light being too close?

Anyway, thanks for looking -- here are the pictures. You can see that I'm just barely starting to see yellowed tips, and the spot I'm talking about is tiny. But these are my girls...

they're getting hungry I feel

Maybe, but I want to be careful -- found this on GrowWeedEasy.com:
That's similar to what I'm seeing, but nutrient burn seems unlikely after nearly 3 weeks in the soil. But I don't want to start feeding and maybe make it worse...

If they're "hungry," shouldn't that show up as a deficiency in some particular nutrient?

theres not much to see

the one red speckle is too little to determine anything
if you begin to see it spread over the entire leaf it could look like calcium def
but I wouldn't do anything based on that alone

the yellowing on the newest growth could be iron def or could be nothing
again its so very mild,, youll need to do nothing and see if it progresses

I DO SEE something else that might be nothing but maybe you could investigate
I see small white tiny specks of almost dust, it could just be the trichs in the flash idk but maybe check for bugs to be sure

I wouldn't feed them yet

a pic of the entire plant might tell more

but I think you might be paranoid lol

Almost all plants get those tiny burnt tips and it doesn't mean a thing. Neither does one tiny necrotic spot on one leaf.

Is this your first grow ever?

When you start trying to fix non-existent problems is when you end up with real problems. To much messing with the plants kills a lot more than just relaxing and letting them grow.

Move along. Nothing to see here.

I found a great spot to download FREE POT BOOKS . I downloaded a grow bible first and got lots more. Books looks great and
complete like the real ones I have here. No web site but just a page of links. Just right click on what you want and then "Save Link As" to download so they don't open first as many are 50+ megs. They got lots. Enjoy.

Many thanks -- yup, first grow indeed. Okay, I will chill, keep an eye on it, and not worry unless there's more to see. I'll snag a picture or two tomorrow of the whole plant and post it. And I see what you mean @im4satori about the white specks, but it appears to be just a trick of the camera -- thanks for taking such a careful look. And wow, @OldMedUser -- that's quite a lot of free pot books. Thanks for that, I will definitely be browsing those.