Please help my strawberries

I moved two dirt pots of strawberries to a deep water culture system Sept 30. All were healthy, well producing plants.
They've all dried up but one in the last two weeks.
How is this possible in a hydroponic system? What am I doing wrong and how can I help my last plant thrice, or at least survive?
5 gallon pail, clay pebbles, using sensai grow, air pump and large air stone. I've been topping the solution daily to cover the roots, with no luck.
I have no idea what's going wrong and I've gone from 6 plants to barely one.
PLEASE SEND HELP!!!!!!!