I grew Beefsteak tomatoes from seed. 6 are planted in the garden (covered with styro huts on cold nights) & 10 are still in pots & put back into the (heated) greenhouse overnight on the cold nights. The garden ones first started with the leaves appearing to loose their green colour & turned white. Now those leaves are drying up.

Usually when tomato leaves turn white it's an indication that they got too cold at night, or that they got some sunscald during the day. It's not a disease, and there isn't really anything you can do about it except wait for the plants to outgrow it, which they will do. Be patient, and all will be well.