I think I found the problem. A quick exchange with
@theatrus had me thinking...If one of the probes shorted out, the way I have them connected, it would cause both to have bad readings. I unplugged my probe that is in my tank and the reading for the ambient air probe returned to normal. My guess is the probe finally gave up the ghost, and since I don't have any kind of protection for shorts on my daughtercard I use to connect them to the 1-wire interface, it is causing bad readings on the other probe. I'll be replacing the probe, and plopping a diode or two on the daughtercard, shortly.