Shriveled tops curling upwards yellow tips

[batwood0378]

So my tops are having a slight yellow fringe and also shriveled and curling up just a bit. They seem happy other than this. Any ideas please?

 

[hotrodharley]

Light wattage and distance from the affected areas? Pictures in normal light needed for better advice.

 

[batwood0378]

Light wattage and distance from the affected areas? Pictures in normal light needed for better advice.

the lights are running at 600w currently about 60” above the plants room is running around 75-77 degrees with average 60% humidity

 

[hotrodharley]

Potassium deficiency

 

[batwood0378]

Running fox farm soil with power SI only at the moment. Currently on day 20 veg.

 

[hotrodharley]

Well it’s time to start feeding them.

 

[batwood0378]

Well it’s time to start feeding them.

 

[batwood0378]

Thanks for the input.