Yellow edges starting at top

[Mxrider211]

Hey growers my buddies outdoor plant is got yellow edging that started from the very top fan leaves and is working its way down the plant slowly. Im pretty sure i know what it is but hes stubborn when he thinks he knows and swears its a K deficiency. I wont say what i think it is cuz if anyone agrees with me he say that there just jumping on the band wagon. So all u pros out there chime in plz

 

[Mxrider211]

Oh ya and the top leaves are the only leaves effected all lower n mids are happy and healthy

 

[Mxrider211]

Its getting worse working its way down from the top. Its not just the edges n tips its in the margins too and now theres brown spots like a p def. Some1 plz chime in here thanks

 

[Mxrider211]

Very top cola

 

[TAngel444]

Dude, I think you need a new friend...

 

[SCM 831]

Definitely a k def

 

[Mxrider211]

Definitely a k def

Ya? Ive never seen them start at the very top n work its way down but ive heard it b4, i checked his soil ph and it was on the low side about 6.1 most spots 5.9 in a few i was feeling more k lock out as it started rite after he top dressed with some bloom nutes