Please help! leaves are turning brownish orange and are drying out?

Growing in a hydro system. Plants been in there for exactly a week and at first looked so healthy. Went in one night to check on it and the leaves were brownish yellow. Now they are dry crunchy and dosent look to be growing. What is the cause of this and what may i be able to do to fix it? Also i have another plant that the leaves look like there turning some sort of blackish color but when looked at under microscope its a really dark green with alot of crystal looking things? Anyone? Please help! Thank yoouu

What's your medium, nutes, ppm, ph? how often do you feed? could use more info.

you need pics for a diagnosis. But im going to guess that youre feeding to heavily. Less is more when it comes to nutes. Dial them back as much as you can. Only add more if you start to see a deficiency.