K deficiency?

[Virandell]

Hi everybody I have a problem for about 3 days after changing the light to 12/12 the 3 CBD plants has yellow tips mostly on new growth is it a k deficiency ? Whole grow I just feed 2 times with nutes and couple of times calmag foliar with 4.0.0

 

[Bobthe420Builder]

Why are u not feeding them

What medium us it

 

[Virandell]

I feed them 2 times 1 time with fish hydrolysate and 1time with biogrow (4-3-6) and soil is a light mix