Sick plant HELP!!!!!!

[Icefisher]

Hello all, I have been getting great information from many who frequent this forum.

I have been growing now for about a month two types of tomato plants using a DWC approach. The two varieties of plants are Sunsweet, and 4th of July. The Sunsweet plant is doing SUPER!!!! and has many clusters of flower buds on it. The 4th of July variety is struggling. It was growing great, but all of a sudden it seems to have stunted, The lower leaves are getting some splotching, curling under and then drying from the tips toward the stem and dying. This is causing whole leaf clusters to die. I changed out the nutrient solution a couple of days ago and thought that I had solved the problem, but, that is not the case. The central trunk of the plant seems to still be thriving and in fact has developed a cluster of flower buds, but I fear that the plant is not going to make it. The PH of the nutrient solution is 5.9 and the Nitrogen concentration is at 200 PPM with an EC of 2.18. This nutrient solution is identical to the one that is feeding the Sunsweet plant. As soon as I figure out how to attach photos to these posts, I intend to do so. Until then I hope that someone out there can help solve the problem using my written description.

Thanks
Icefisher