A fifty watt bulb on a 10 gallon tank will give you a hot spot directly underneath the bulb of about 95 to 100 degrees, possibly more.

I don't recall seeing what you were using for bedding but my guess is you cooked these guys. With a UTH pad you need at least a couple of inches of bedding above it and you don't need more than 25 watts with a corn in a ten gallon tank.