Thanks for the info. I am a MJ Passion morning guy most of the time, as I am out the door and 100 miles and running everyday. I will try to respond as fast as I can.
The GE Timer seems to be cool, I personally have never used one, but I see no issue with it, that should be fine.
So your usuing H&G Coco nuit line. I have never used it, but once you learn ppm then pretty much any nuit line should work fine.
One thing I noticed was that you use R/O water. Whenever usuing RO water, you MUST add Silicate and CalMag BEFORE any other nuits. There are a few different CalMag nuits out there, so mabey someone could chime in what works best with H&G nuits.
I am a little scared to offer nuit advice usuing Coco, as I have never ran coco. I have heard and seen too many horror stories about Coco. I see alot of inconsistencies with that medium. Sometimes folks hit it good, and other times thier plants burn up. All I can say is ensure you have Calmag added to your mix when running RO, I can't stress this enough.
Man, I almost want to say don't run CO2 the first run. It would benefit you more if you pulled out one click without it and ensure that you can control all the room conditions first, such as Temp/Humidity. This is a MUST.
Your day temps of 77 is great, and a 4 degree swing is ok. I like a good 10 degree swing from day to night myself. Humidity should be around 60 for veg and first 2 weeks of flower, then drop the humidity to 50. Only panic if the humidity is higher then 65 during flower.
If you think you have a good handle on your nuits and understand PPM's AND have the room dialed, then CO2 would benefit. I personally have been running CO2 only during Veg and the first 3-4 weeks of flower, then I go back to atmospheric elevations (around 400 ppm).
So, before we go further, Are you going to start over with a new batch of clones? This would be a great start then tryin' to bring back to health messed up plants...trust me. You will save more time and money by starting new, weather it be clones you have taken or new ones you bought.
I have an article about CO2 somewhere on the boards here, that would be a good read I think.
More to come.