I have four tomato plants, three of which are together in one area and the last one by itself in another area. The three that are together have been looking sick recently. Their leaves used to be flat, but now they're kind of curling upwards. My other tomato plant that's by itself has perfectly healthy foliage and looks great, but these ones don't. When I shake the plants a little, I can see little white bugs flying from underneath the leaves, but there aren't that many. Should I be concerned for this leaf curl and these bugs?