I know you say it isn't a light issue, but have you tried to raise your hood a couple of inches? It really looks like the lights are too close to me.
Agoblue97 Reviewed by Agoblue97 on . nut problem yellowing and dying leaves..PICS 4 weeks into flowering ph 5,8 ec 1,8 77f day 68 nigth 40 rh average hydro with clay pebbels 600w all in all good conditions expekt in late veg and 2 weeks into flowering when i had it to cold at nigth 58f. are now 12-14 inches tall thats way to short. probaly because the cold,the ladies thinking winter was comming(started to bud at ons i started 12/12 also).worst areas is those resiving most light but it is not high temprature under the light. can anyone tell me what my prob is? Rating: 5