DIY can get you sometimes. I had the same thing happen to me in a 29g tank where the CO2 went from about 20ppm to 140ppm overnight. It's a bit safer with pressurized since you have full control of the injection rate.
I've been running at 50+ ppm for several months now, with no noticeable effects. I'd guess what really hit you was the rate of change (e.g. if the CO2 levels jumped that high over a 1-2 day period) versus the actual ending levels. My opinion, anyways!
46g bf, XP3 w/ vertical spray bar, CO2 w/ SMS122 & diffuser,100% Flourite, 96w+55w cf AHS, AGA Member