* Spots (pic 4), on only 3 leaves of the plant at ...

It is a slight nutrient burn. When you say that you are feeding 0.6EC (PPM 300) that's total strength of the solution? Or plus water? Second, feeding frequency. Even if you are feeding low strength, if you feed too often, that also can lead to nute burn. Feed only once every 7 to 10 days, no more in soil. Third, sometimes plants react badly to foliar feedings, so don't do it. Hope that helps.

Hey there so over all your plant looks very nice and bushy. I do see the burnt tips and spots, I think most would attribute to a nute burn, or occasionally if a light gets to close it can burn some tips. Be careful of leaves that rest on each other as they'll hold that water there that you're misting, and a variety of things can happen like mold spotting etc. Also you may be ready to be transitioning to the blooming nutes,if you haven't already. And sometimes those burnt tips won't go away but if they stay the same and don't increase I wouldn't worry too much. Happy growing and love the plant. :)

Could be a watering issue , test the runoff ph and EC , if it’s more than 2 it’s too strong and if the ph is below 6 or above 6.8 it will need sorting 👍

That is nute burn! I would feed her plain water until the problem is fixed.

You have slight nutrient burn thats why your tips appear burned. Also if you're spraying and lights come on.. This could be the residue drying from that. But the brown spots look like calcium deficiency. Hope this helps