Presta Valves keep failing
Presta valves are fairly fragile things. It's easy to bend the stem once it's unscrewed. They work by the tube pressure being higher than the atmospheric pressure. This causes the valve to be forced closed. It is not until you either loosen (unscrew) the valve and depress the stem or place a pump on it and increase the pressure above the valve until it is overwhelmed and allows air in.

Point is, you can leave the valve "untightened" and air won't escape. The valve mechanism failed because for some reason it did not return to a closed position completely and leaked out. Then when you tried to top off the tire again it was further stuck Two best guesses:

1) You had a run of bad tubes. Welcome to road cycling. Things are more fragile. This is my first choice. Buy a different brand and see what happens.

2) Schrader valves are more durable and forgiving of rougher treatment. Perhaps you were use to them and when you topped off the presta tubes you bent the valve core and it wouldn't fully return to sealed. 

Don't give up. I've had bad tubes before.

And one last thing: If you are a valve bender (like myself) I found the cure. Silca and SKS both make a chuck that doesn't need to make contact with the valve core. It uses the pressure from the pump to overcome the resistance of the valve core. Here is the SKS version, currently on sale at Saint John Cycles. You just push it on and pump. Couldn't be easier or more effective. Good only for presta though.