plant problems 6 weeks into flowering

Hey, so im running a hydroponic grow with 1000 watt HPS with a few 4x8 tables, 1 table is having some sort of issue i cant figure out what it is, tomorrow will be 6 weeks into flowering, the buds are looking alright, not like the rest of the tables but they seem to be looking alright, but the fan leaves have started to turn brown, dry, curl up and fall off in more than half the plants on that 1 table, anyone know why this is happening or what is the reason for this, i was thinking maybe because maybe its the 1st table right by the beginning and its by the wall its getting bad temperature or maybe some kind of plant sickness or disease, its not all the plants on the table but the middle pack of it that this is happening too, i am thinking of doing a flush on that specific table for about 4-5 days and have the plants just drink water, than i will rez change to my normal schedule. Anyone have any ideas why this is happening, the temp in the room is between 76F-81F during lights on. Please let me know what you guys think

 

also i forgot to add this has been happening about 1-2 weeks ago, tomorrow will be week 6 into flower, also its the sour diesel strain, if you guys think some pictures would help let me know i will upload them.

Thanks Meyer

 

no.... each table 4x8 table has 2 1000 watt HPS

 

sure, i took this picture today which is week 6 1/2 in flower, i also took out 3 plants as they totally died but from looking at this picture do you think the rest of these have a chance? i dont know what it was maybe a root pathogen, someone said that they think thats what it is, but take a look and let me know what you think? i am currently flushing the rez out for 2-3 days i heard that can help solve this issue