Help re leaves

Hello, I need advice please, I'm growing two plants in hydro, my ph is 5.4 EC is 1.2, this is the second week of growth, one plants leaves are turning brown and crispy and now the tips of the other are starting to get dry too.
growing under LED lights in a grow box, temp stays a constant 74...they are auto fem kush.
thanks... Have tried to attach pics but can't seem to do in an ipad...but any advice appreciated..

ph should be 5.8 in hydro

if you have not read this you need to

https://www.rollitup.org/dwc-bubbleponics/234626-rosemans-diy-bubbleponics-tutorial.html

Thanks Commander Strax ..