Hi, It looks to me like it may be Tomato Spotted Wilt Virus (TSMV). This is usually spread by thrips. The disease is fatal. You can control thrips by using yellow sticky traps. For more information you may look at the 3rd thread in this section of the forum, Common Garden Diseases and Pests. Titled tomato spotted wilt virus.
http://www.tomatoville.com/showthread.php?t=1519
It also could be a burn from your spraying. Did you spray in full sunlight or in the evening? If the leaves were wet while in full sunlight this could be a burn from the magnified sun.
Did you check the undersides of the leaves for insects before disposing of the plants? It is possible that it could have been some kind of insect damage.