Whew! I'm so glad to hear that's all it was, and it sounds like you've got a good handle on the co2. The trouble with these little boogers is that things can go south in such a hurry, I just didn't want to take any chances and then feel bad about sitting on my hands later. I'll relate a little story of my own, which explains why I get exciited/worried on short notice. This has been years ago, but one day I noticed one of the big discus looking a little 'funny'. Now I was about to head to the airport (3.5 miles away) to pick up some fish, so I thought to myself that I'd better check the water params when I got back to make sure everything was ok. By the time I got to the airport (about 15 minutes) I got a call from my wife telling me that all 6 discus were doing the 'death spiral' but the dither fish were fine. I had her net 'em up, dump them in the nearest available tank (temp and params be danged) and I headed back. When I got there they were PO'd from being scooped and plopped but upright and breathing, and the other fish in their tank were just fine. To make a long story shorter, apparently the tank had built up a anaerobic bacteria bubble under one of the pieces of bogwood and one of the plecos disturbed it probably just shortly before I noticed the discus looking 'funny'. pH bottomed out, nitrate spiked, and the dissolved o2 dropped drastically all in a matter of minutes. Now in a 'regular tank' with 'regular fish', this sort of thing happens all the time, but since other fish aren't so fussy, the aquarium balances itself back out, the water gets changed, and nobody knows it ever happened. With discus... well... Which is why the most paranoid discus keepers do 90% daily water changes. I don't, but I know people that do.
Anyhow, I'm just happy it was a nothing, I'll try not to jump too quickly next time...
Scott