Tops yellowing late in flower after smooth sailing entire grow

[TWINTURBODOGO]

So have 1 Lemon Skunk sativa in late/mid flower, roughly week 8-9. She has been great until about a week or so ago. <br />
She started showing some yellowing of the top leaves and some middle leaves.<br />
Now a few top leaves are showing some purple too.<br />
She was drinking 3/4 strength mix at 980ish ppm. <br />
But since the yellowing of leaves started. She has stopped taking up nutes and just drinking water. <br />
My ph has been stable just like it usually is. 6.5-5.6. I don't have ph problems. <br />
Could it maybe be magnesium deficiency? <br />
<br />
Dwc, 5g of water. <br />
Botanicare KIND nutes<br />
Ph 5.6-6.5<br />
Under cob led lights <br />
75-90° 50% rh<br />
<br />
Not sure what the problem is. There is no reason I can see that there should be a problem. <br />
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Thanks for looking!

 

[AnimaSola]

Looks like a re veg, do you have 12 hours of total darkness at the same time every day? Can you see any light in your flower room with lights off?

 

[AnimaSola]

The brown parts look like bud rot, never foliar spray a flowering plant.