Everything gets fungus in Texas. What a pain in the tookus.

Early Blight Early Blight can affect the foliage, stems and fruit of tomatoes. Symptoms: Dark spots with concentric rings develop on older leaves first. The surrounding leaf area may turn yellow. Affected leaves may die prematurely, exposing the fruits to sun scald.

Gray Leaf Spot Gray Leaf Spot affects only the leaves of tomatoes, starting with the oldest leaves. Symptoms: Small, dark spots that can be seen on both the top and bottom surfaces of the leaves. The spots enlarge and turn a grayish brown. Eventually the centers of the spots crack and fall out. Surrounding leaf areas will turn yellow and the leaves will dry and drop. Fruit production is inhibited

Late Blight Late blight affects both the leaves and fruit of tomatoes. Late Blight is the disease responsible for the Irish Potato Famine. Late Blight spreads rapidly. Cool, wet weather encourages the development of the fungus. If you suspect you have Late Blight, contact your Local Extension Service for definite ID. Symptoms: Greasy looking, irregularly shaped gray spots appear on leaves. A ring of white mold can develop around the spots, especially in wet weather. The spots eventually turn dry and papery. Blackened areas may appear on the stems. The fruit also develop large, irregularly shaped, greasy gray spots.
Early blight sounds like the right timing.

Try Actinovate.

I tried it on my cherry tomatoes last year and they really thrived without any problems. Actually, the only compliant was that it produced so many tomatoes that I had to give away to everybody.

I forgot to get actinovate this year but I used Biozome, seaweed, molasses, fish fertilizer and myco fungi product this time and so far, they look to be very healthy.

Here is a link that might be useful: Actinovate

I can't tell exactly from the picture, wish we could see a close up to get more detail.
Here's the link to the A & M tomato problem solver, maybe this will help.Good luck!
Susan

Here is a link that might be useful: A & M Tomato Problem Solver

This early in the season, I really want to say it's just overwatering... but you are in a raised bed. Vermiculite retains a lot more water than other similar soil amendments (perlite or expanded shale), and combined with peat and compost.. it could be causing problems for such a small plant. Check to see if the soil is waterlogged - if so, let it dry out before watering again, and try 3 tbsp of 3% hydrogen peroxide per gallon of water for the next few weeks.

Overwatering related yellowing is thought to be a result of acute iron deficiency - under water logged conditions, the plant can't absorb and utilizer iron. Thus, a foliar feed with iron chelate and other minerals may help as well.

Good luck figuring it out, and if worst comes to worst - it's still early enough to put in a new plant... thought I know how much that can hurt.

I'm pretty certain that's overwatering. Small transplants don't use much water and can be easily overwatered. Let the soil dry out and they should recover. Water deeply once a week, and twice a week when it's really hot and dry and your plants are large.