I've got 3 Better Bush tomatoes, & 1 Better Boy plant. They're all about 5 feet tall; thick & bushy & loaded w/green tomatoes. In fact I picked a few small "pink" ones this morning. But, 2 of the Better Bush plants have started getting yellow leaves. At first, they would yellow & then turn brown & dry. But now they're just yellow. I did just fertilize them 2 days ago w/fish emulsion out of my aquarium filters. And there's granulated tomato food that I put in the ground when I planted them. I noticed a few days ago, that when I was working around the plants, there were these tiny, tiny white bugs...smaller than gnats. I sprayed the plants the next day, in case this is what's causing it. I've heard that you can get a virus in the soil; wondering if this is it. Any input would be appreciated. Thanks!