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.

I'm new to gardening and hydroponics, but I am successfully growing Black Seed Simpson and Red Romaine using the General Hydroponics Flora Series. I mixed the nutes as it says to below, as found on their website's FAQs section: "The proper ratio of each Flora Series nutrient depends on the crop and the stage of growth (look on the label for specific recommendations for different crops). However, as a rule of thumb we use the "1-2-3" ratio: For seeds, cuttings, or delicate seedlings- use 1/4 tsp. of each nutrient to 1 gallon water For the vegetative stage of growth- use 3 tsp. (15 ml) FloraGro to 2 tsp. (10 ml) FloraMicro to 1 tsp. (5 ml) FloraBloom to 1 gallon water For late vegetative to pre-bloom stage- use 2 tsp. of each nutrient to 1 gallon water For bloom initiation to ripening stage- use 1 tsp. FloraGro to 2 tsp. FloraMicro to 3 tsp. FloraBloom to 1 gallon water." in your case, I'd mix them using the second mix (vegetative stage) but maybe a bit lighter, and see what happens. Other things that effect how much nutes you need: temperature, the amount of light, and pH/PPM. Although your lighting is rather sufficient. Plants require less nutes when it's hotter, and more when it's colder.

The best answer to your first question is an "educated guess" based on research that I have read regarding uptake and internal plant concentrations of specific nutrients. Let them spend their money on lab testing and whatnot. There's actually quite a bit of info out there from university ag extensions. And then from about 6 months or so of my own anecdotal tests adding specific elements to buckets and seeing how long it would take to deplete which in itself can be meaningless since plants will uptake certain elements even when they are not needed which can interfere with future uptake of needed elements but combining everything together with the fact the some elements are stored for future use and taking note of what the plant is telling you, leaf and fruit diagnosis, you can get an idea of what is needed and being used. Plus certain elements are taken up faster than others. If you start with a well balanced 500ppm solution and let it run a plant is not going to uptake it all equally meaning in two weeks or so you won't have 0ppm. The ppm, or EC, of the solution will bottom out at a level where everything the plants can uptake has be taken up leaving the less needed and slow uptake elements. Put that all together with some other stuff I haven't mentioned because it gets confusing very easily and one can make an educated guess which seems, thus far, to proving good. Luckily there is a built in margin for error since plants can handle some imbalances just fine if they occur. This mostly applies to larger fruiting plants that have greater needs. The Kratky method where you never top off or add nutes shows that you can run a res for a month, for something like lettuce, with no additions and have no issues if the solution is well balanced to start. Try that with a fruiting tomato plant and in about a week and a half and your solution will be basically depleted of anything the plant readily needs. It'll survive for a bit on stored elements but then will show signs of deficiencies pretty quickly. I see it on quite a few plants that people show here when they are trying to do too much with Kratky. But I digress. That sounds really expensive for an air pump with that low of an output. If you ever go a different route you can surely find something better online. I use 2-inch air stones in my buckets that are $3. There's definitely an outlay to start a decent hydroponic system and frankly after running costs are tallied you're lucky to break even as compared to just buying it at the store for most plants but it's nice to walk into my room and grab some tomatoes and herbs and go cook and not be needing stuff like that and have to run to the store or have it go bad and be completely wasted sitting in the frig. Plus, it's a relaxing hobby. Anyway, my fingers are tired from typing.

This method seems VERY SIMILAR to the german self watering pots I use. you put your plants in the top and then the water reservoir is in the bottom. they use what is called pon as the soil - similar to gritty mix (no net pot). the roots grow very quickly. they are called lechuza pots and are kind of pricey. they work for not only adenium, but also for african violets. there's a water level thingie that tells you when to water. you also may purchase the pon substrate separately. No. 2 chicken grit and Napa floor dry (part No. 8822) also works. i like the mini deltini this is the taller (not mini) deltini dave