What's going on with my Jack H

[ElementsOfLife]

Week 5 of flower, organic grow. Tops dressed on week 4. I water at 6.8 using PH down . 280 true watts led at 15" .

Plant is yellowing from top down and tips turning purple.

 

[Gshoo]

This thing happened to me with Northern Light auto in the last two weeks of flowering. I think I red somewhere that it’s nutrient deficit.

 

[ElementsOfLife]

I'm hopping it's just nitro, gonna make up a tea and hope it helps but I'm already 5 weeks into flower I'm not sure it will help. I guess I'm just worried it's salt build ups from using PH down when watering and I'm getting a lockout or something

 

[HugePeckerhead]

I know plants tend to use less nitrogen during flower then veg. I've also read that many times yellowing of the leaves during last few weeks of flower can be normal too.