Still not sure, is this nute burn or defiency?

I still can't figure out if this is being caused by nutrient burn or deficiency and it has started on every plant now, kind of annoying....I am growing in soil using entire house and garden line up and feeding them with the aggressive strength nutrient feed regimen and water is ph'd to around 6.5 to 6.6 every time I water and has never left that ph range. The plants are into the 7th week of veg under an 18/6 light cycle, switched to 18/6 about 3 weeks ago. I flushed about ten days ago with a flushing agent as part of my monthly flush routine. Also I am having trouble keeping my humidity about 25% since my inline fan sucks all of the air out of the room rather quickly, but I feel as if I water enough for this not to be a problem.

So any advice on what this is and what its cause could be would be very appreciated.

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ur over feeding - darkened leaves with yellow tips are indications of too much nutes.

Gotcha, I'll flush again and back down on the ppms, I was planning on throwing them into flower this Sunday, should I wait another week to give things time to balance out?

Dont flush!

yes - u want them in the best health possible before flipping the lights

lay off the nutes for a while but supplement your ph'd water with a stress reliever such as superthrive

Why do I want to NOT flush? I thought that was standard procedure for nutrient toxicity? If I add in superthrive, how long should I lay off nutes for and to what degree should I lay off nutes?

You burn is fairly light. No need to flush just lay off the nutes for a few.

the plants recovery will indicate when the nutes have balanced out

It was a case of nutrient burn coupled with a calcium/magnesium deficiency....I flushed the girls and started a treatment of calmag and they are already looking better...hopefully they continue to improve

You said humidity was 25%? That is contributing to the problem significantly IMO. When humidity drops below 40%, plant cannot transpire toxins and nutes well causing toxic buildup. Get a humidifier or put wet towels in their or foliar feed with plain distilled adjusted to 6.5