Please Help, what caused this?

Thread starter #1
Okay so my leaves are turning yellow/brown and look really dry. Please any feedback will help.
I using FF Ocean Forest, so could it be nutrient burn.
These plants are close to 3 weeks old so the two small ones are definitely small.

 
yes i agree ph meter is needed . u can get a cheap yellow one off ebay for 10 bucks , just grab some 7.0 calibration fluid also .