Okey dokey I already see some things that could be tweaked.
First let's talk Magnesium. I don't know about the GH 3-part and its Mg problems, but I would hesitate to add Epsom salts to your res!!! You're right, that is kinda eek. If you like epsom salts as a means of Mg delivery, make a spray bottle up with 1/4 -1/2 teaspoon, a quart of water, and a drop of liquid dish soap, that you can lightly mist onto the leaves if you see Mg def signs, whcih look like distinct pale stripes between the veins. Not bright tan dead stripes though; that's something different. CalMAg Plus is also GREAT and if you look at the sticky in hydro called 'Latewood's Legacy', there is a great discussion of the GH 3 part as a grow tool.

Next your ballast! If you can get it up on a milk crate or at least a little off the floor, awesome. If you can put it OUTSIDE the grow area, awesomer. Ballasts give off a lot of heat.

The hood! Yup it is air cooled. So is the other end- the one we can't see in the pic- is that open to the room, or is your light on its own closed circuit and not exchanging air with the plants? Is there any way to make the curves in your ductwork smoother, or even straight? Turbulence within a duct will definitely cut into your total air flow! Do you know the CFM rating on your fan, and where is it in relation to the light, and to the exhaust ducting? A strong fan (100-300cfm) that is set to suck air through your exhaust is a must with a big light in a small space.

Gotta run, will check back later.
stinkyattic Reviewed by stinkyattic on . yellow spots. pics yellow spots. a couple weeks old and have gotten a little worse. nutes at about 1/2 strength. ph=5.6 plants are 5 weeks and a day old. temps are high...around 90 during the day and 74 at night. running a 1000w hps with exhaust fan and portable a/c in room. need help. thanks in advance. Rating: 5