Yeah I would guess that too, also since nute burn normally would only affect the tips...and light burn wouldn't just affect the edges.
You are using organic nutes, and these supply nutrients slower to the plants than "chemical nutes", because with organic nutes what you're doing is feeding the micro organisms to condition the soil, rather that providing nutrients to your plants directly. So a deficiency there is MORE likely.
I did one run with organic nutes once, but I wasn't too impressed really. I like "normal" nutes better since I just feel I have more control over what I give the plants. Especially if you have a def....then you would need to supply the required nutrients fast..and that's actually not possible if nutes are truly organic. So you MAY possibly want to look into "normal" mineral nutes if you want to fix this problem fast.
That being said, and it doesn't even matter what exactly the deficiency is, you should ALWAYS flush with pHed water only (6.5 for soil) if you see something odd going on, and then give the proper dose at the correct pH. Normally this should fix things. You can't make things worse with flushing.
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with weakened mix
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With organic nutes it is very difficult if not impossible to overfeed. So this is likely your problem right there. Flush (just because

) and then give full-strength. This is what I'd do.