Like terrybull said, it's more than likely wind / sun burn. Seedlings need gradual introduction to wind, the same way that they need gradually introduction to sun. The wind bends the stems and leaves and also pulls moisture away from the plants. The "hardening process" of gradual introduction to wind allows the plants to react to the increase in bending / lack of humidity by thickening the stem and developing tougher outer surfaces of the leaves.

Are these the leaves on the lowermost branches, or in the middle/top of the plant? I have leaves like that on the bottom of most of my plants, but from the middle up they look perfect, and I always figured that was natural. But then again, I'm a total newb.

It`d be pretty easy to overdo the misting in a fence post as most of it will hit the wall and flow down.to the bottom of the pipe, When the roots get large they tend to restrict the drainage and they end up sitting in water. that isnt moving very fast. I guess you have a nozzle between each plant site? I would turn off the mist and time how long it takes for them to show signs of wilting. Turn the mist back on until they stand back up. then set the mist duration to 1 second and set the pause duration to half of the time it took for them to wilt. If they start to wilt cut the pause time in half again after you`ve got them standing back up. After a few iterations you`ll find the ideal settting. Its best to fix the mist duration and just vary the pause so they get many short mistings rather than fewer longer mistings. ie; aim for little and often

Please don't assume you have some nutritional deficiency without getting a soil test. Blind fertilization, especially for minerals, is like firing a gun with your eyes closed. Epsom salt as a generic fertilizer is a myth, UNLESS you have a magnesium deficiency, which is rare. Have you gotten a soil test? If you had no mineral nutritional problems last year, you probably don't have any this year, and the fish emulsion should do a good job for nitrogen. I would make sure the soil is moist, by sticking your finger in deep. Drip systems are good, but they make it hard to establish how much water your plants are really getting. If no insects are obvious, and moisture isn't a problem, I'm going to guess fungal infection, perhaps blight from new soil. I assume you're not using any anti-fungal preventatives. Principe Borghese is an heirloom, and those are notoriously unresistant to fungal infections.