re: Need tomato help! What's wrong with them?

Looks/sounds like a water problem to me. Over or under watering? Does 5 gal. pot have one or more holes at bottom not entirely on concrete so it can truly drain? I have had pots in the past being entirely on concrete and pretty much "sealed" at bottom so they could not really drain water reasonably as necessary.

2" gravel at bottom is great, but the composition of your soil above that determines % water/moisture retention vs. time. Absorb that for a minute.

Thus, no hard and fast rule about how often to water. Especially since daily temps increase as we get into the late spring, early summer - not to mention cooler, rainy days.

Old timers like my brother and I (around 70 years old) both rely on "new fangled" gadgets like Moisture Meters (Dr. Meter or equivalent - I'm not a salesperson). Less than $10 each, no batteries required (rely on a 10" probe to determine dry to wet moisture on a scale of 0 - 10 galvanically).

I would think you youngsters would be more in tune with electronic devices than us oldsters - j/k, trying to help. This little device absolutely helps to determine when your soil is dry - or not. Thus when to water. Available online, elsewhere.

Calcium and fertilizers like Miracle Gro for one of your "waterings" maybe every 3 - 4 weeks can absolutely help. Do not over fertilize 1st year of soil in your 5 gal. pot. 2nd year mix in Bone Meal and fertilize more often with your next tomato plant. JMO.

If successful with growing some tomatoes, watch out next for plant destroying pests like tomato hornworm. Use Bacillus Thuringiensis soon as you notice eaten leaves.

Good luck to you. Hope I helped.