Nice, I'm trying CO2 in my space right now with some mushroom spawn bags. The Exhale bags are just yellow reishi spawn; I grow king oysters and winecaps anyway, so I've been throwing about 10-15lbs of colonizing sawdust spawn in autoclave bags in the floor of my tent next to my containers. Seems to do more than nothing, but I've not gotten a meter to measure how much it increases CO2 in the space. Interesting to hear you run so much light at atmospheric CO2, I would have thought above 1100-ish you would see diminished returns without some supplementation. I guess that's the benefit of so much air exchange, it's likely never far below ~400ppm.