Welcome to the wonderful world of growing tomatoes in containers. Here is what I've learned over the years. You water them too much, they wilt. Water too little, they wilt. Potting mix drains too quickly, they dry out too fast, they wilt. Potting mix retains too much water, their feet get soggy, they wilt. Fertilize too much, they wilt. Fertilize too little, they wilt. Give them a funny look, they wilt -- and then produce tomatoes with blossom end rot.

Check the underside of your leaves for webbing. It is possible you have spider mites or a leaf curler. If you find webbing (or other signs of bugs), spray the leaves (top and bottom) with Neem oil. Also, if you are still getting a lot of rain, spray the underside of the leaves with a sharp stream of water from your garden hose while it is raining. ~james

Old topic but wanted to share my input. I'm growing hydroponic tomatoes (various strains) at university in a lab setting (indoors under HID lights) and outdoors in a greenhouse. In one of my greenhouse NFT systems, i recently had a similar problem on 1 tomato plant (total 9 plants that share the same res and tubes). But im gonna try to diagnose your issue by mentioning what others missed out on. 1 major cause of leaf curl is compaction of root system (i.e. roots are compressed or dont have enough space to expand). This risk is exacerbated in hydroponic systems that use tubes. This was the problem i had and had to replace tubes with square tubings that have a liftable top. Once you have access to roots, you must seperate them strand by strand (i.e. so they arent sticking together). In your setup, this risk will further be exacerbated because you filled the entire pvc tube with hydroton (right?). Remove hydroton from tube and place the plant in a net cup with hydroton. Nitrogen burns usually cause browning/yellowing of leaves (similar to sun/heat burn) and not purpling. Test your solution for each chemical if possible, or use a commonly employed aggregated measuring device that shows total concentration in ppm (dont let it exceed 2500). In my system, only one plant was affected. Coincidentally, it was the largest of all plants with the most root mass. I let another normal one grow to its size to see whether it would undergo the same problem, and it did. Viral and bacterial infections that cause leaf roll usually cause it to roll up. Same with the physiological roll. If your leafs roll down AND if your stems bend, this is caused by a diminishing turgor pressure (read: not enough water reaching afflicted area). Mist several times when lights are off (no photosysnthesis) and observe increasing turgor pressure (unbending). Or, untangle roots and remove hydroton from from pipes. I tested various growing methods including fully and partially submerged roots. They all work but a submerged root cannot intake oxygen; it has to borrow oxygen from another part of the plant (i.e. a root part that isnt submerged or above ground stem). This requires energy for transportion and isnt the most efficient (optimal) way for growth and cellular processes. Lastly, an airstone in the reservoir is useless unless the reservoir is completely airtight all the way up to the plant holes. Better to keep small airstones in the pipes right under the plant roots. Those that say aerating the res prevents bacterial development.. is false. If you dont have air in res, you will get anaerobic bacteria (they grow/accumulate slowly but acidify the solution); if you have air in res, you get aerobic bacteria (not acidifying but grow extremely fast). Most bacteria prefer aerobic environments for optimum growth.

Britt, I agree with everything Jay said. Most of the time physiological leaf roll is merely a stress reaction, and the extreme heat is likely the cause. The last thing I'd do is repot them unless they're in small containers. Repotting would be stressful and the plants don't need more stress. Tomato plants generally do best if we leave them alone and let them grow and take care not to 'love them to death' with too much water and too much fertilizer. Having mentioned fertilizer, I'll add that it is much harder for plants to remain well-fed in this heat if they are in containers because the necessary watering leaches the fertilizers out of the soil. So if, by chance, your plants are in smalish containers that require a lot of watering, I'd take great care to ensure they are well-fed. I'd probably feed at least weekly in this heat, or maybe twice a week depending on the container size, but I'd cut the fertilizer strength in half so it is weaker to make up for the fact I was fertilizing more often. When you feed container plants with a water soluable fertilizer, their roots take up what they can and then the rest of the fertilizer often is washed out of the soil the next time you water. Shade may or may not help. If the temps are going over 105 or so, the shade doesn't help as much as you'd like because the poor plants are still so hot in the shade. If the plants are getting reflected sunlight and heat from pavement or building walls or a wooden fence, moving the containers so they are placed in a cooler area away from heat-reflecting surfaces can help. If your plants are in the ground, making sure they are well-mulched will help keep the soil cooler and that might help with the curling a little. I looked at the bare soil temperature map yesterday and it was showing a temperature of 111 degrees in my county at the time I looked at it. That is why mulching is so important--because the soil is so very hot right now and the roots are just baking in that hot soil. Honestly, though, in a summer like this, there's going to be a lot of leaf curl in the heat and that's nothing much you and the plants can do except tough it out. Sometimes leaf curl is a symptom of a disease or pest issue, but 99% of the time it is just stress. I'm so used to seeing leaf curl in hot summers that I rarely even notice the leaves are curled unless someone else notices it and mentions it to me. Then I shrug my shoulders and say something like "Oh, that's heat stress. It happens every year." Dawn