This is 1.5 weeks into flowering in a 4x4 tent. The temp stays at 77 and sometimes rises to around 79 so heat is not a problem. I don't understand what is going wrong. I have an 8 inch exhaust at 720 CFM. The HPS is around a foot and a half to two feet away. Im not over or under watering. What could cause the top leaves to curl like this?
I looks like a lack of air flow over the leaves. What is your tents humidity? What is the temp above those curled leaves? I should add. When ever my plants are curling at the top but not the bottom, I've found there to be a lack of air flow in that area causing the air to heat up and the humidity drops. I leave a temp/hum gauge hanging from a piece of rope in between the plant canopy and the light. Floor temp can be 77f 45% and the air between the canopy and light can be as high as 95f 30%. Even with high CFM blowers/fans, there can still be dead spots.
The air in my tent is replaces entirely at least 7 times per minute though. My exhaust fan is overpowered for a 4x4 space. The humidity is around 48-50%. The temp stays at around 75 most of the time.
A blower may read 720CFM's but I can promise you its not. There are just SO many variables. Here is a great website, depending on your ability to accurately measure your grow conditions. You may find your 720 SCFM fan be 400 ACFM or less. SCFM vs ACFM | Standard CFM vs Actual CFM | pdblowers, Inc. Temperature Room pressure Actual pressure Humidity As well as the filter and tubing. Could be a PH problem though. Maybe someone else can chime in with some ideas