Do you have any pics? if they are pointing to the sky that usually means the light is too close/intense. depending on heat it can also mean heat stress as well. they try to shade themselves basically cause too much light/too hot. as for being light green/yellow again hard to tell but they really shouldn't be dark green. lime green is alright imo but without pics hard to say. my best guess for this is whatever medium your using has little to no nutrition. again post some pics for better answers if you can post pics otherwise right now it's just a guessing game of what could be the problem. LOTS of issues can occur with same symptoms.