What's the point of the chiller and the air stones in the res? I thought the whole point of DTW was that you DIDN'T need a chiller, or have to worry about constantly checking pH, etc... I'm on my second bloom atm, in ChowMix DTW Drip, and have seen no problems due to root pathogens with res temps in the mid-upper 70's and room temps in the upper 80's low 90's. In fact even when my plants were at their worst I pulled a couple out of the pots and the roots were as healthy and as white as can be!
Definitely looks like a nice setup, and well thought out, I just am wondering about the benefit of the chiller/air pumps. I've also read pumping air into the res can fuck with the pH over time, even with just salts and RO water.
Keep up the good work, and remember that what goes around comes around. I'm sure your grower friend will return the favor handsomely for that beautiful Critical you gave him!