Yellowing in a few different places

[pulchripes]

I've been doing light sprays of epsom, the lights are 2x 120w LEDS in a 4x2 tent

 

[pulchripes]

This is them today

 

[pulchripes]

Is this now potassium deficiency? Thought maybe nute burn but PPM is only like 900, I'm using grow 1 blend for stretch period, yet to use bloom 2 designed for post stretch and I think now at 4 weeks the stretch has stopped