HELP with new plants in my mothership roommate

These are my four plants, 2 kandy kush and 2 blz bud, one of the blz's has a yellow tipped leaf on both sides, what might be the cause of that? and can i clip the tips of them to get rid of the yellow leaf. and the other kandy kush is very undeveloped and growing very odd looking, this is as close as i can get to them with my camera. help is appreciated!

also my ppm levels are 240 i need to add some water to dilute it a little bit tonight. but take a look at the last pic i am very worried about this plant it def. doesnt look normal

someone feel free to say something i wouldnt need help if i didnt post this

hey i have a mothership/roomate two and its my first time using it and i have 4 big buddah blue cheese clones going. Did you ever get this problem resolved? i wish i could help but im new to this as well and its my first time doing hydro. Do you have any advice for me using the mothership?