First time grower going through the ''first scare'' ritual.

[josevi]

So, I am a first-time grower growing 9 plants in a 0.8 x 0.8 grower (yeah, that is a lot for the space I have...), and right now I am literally going through the first problems with my plants. One week ago I noticed some fungus gnats and started to spray them with neem oil, which seemed to work. Today, I woke up and went to do a check-up, and noticed some things. My smaller plant, a CBD one, has some marks on some of its leaves. After some searching, I borrowed it down to LEAF SEPTORIA and immediately cut off the parts affected by it (tbh, I am still not sure if it is leaf septoria). Then, when I checked the other ones, I started to see other problems. Besides the signs that my CBD plant showed, some of them are a light green between the veins (which makes me believe that it is MAGNESIUM or MANGANESE deficiency), others have some brown spots in the middle of the leaves (which makes me believe it is CALCIUM or MANGANESE deficiency), and a few were with some weird shapes having their edges curling down (I have no idea if it is a problem).

I will upload some (a lot) of photos just so you guys can get a better understand of what I am trying to describe and I would really appreciate if you guys could give me your insights on what you think it is since right now I am on the verge of panicking (I am not even joking lmao).

Once again, really appreciate any insight, and thanks for any help!

 

[Beachwalker]

I don't see septoria

 

[Jimster]

It would help a lot to included a list of the growing medium type and composition, feeding schedule, what you are feeding, as well as a bunch of other factors. Neem oil itself can trash a plant if applied incorrectly. Deficiencies are actually pretty rare if you are using a commercial growing medium. Too much food can cause issues as a toxicity, but also by inhibiting other nutrients, better known as nutrient lockout. If the Ph is out of whack, the plant won't be able to absorb the needed nutrients. Adding more will only compound the problem.
As you can see, growing can be a brain scrambling experience. Post your updated info and I'm sure more advice will be coming, but you need to provide details to help eliminate what the problem isn't.