Plants Under Stress In NFT Tubes

NFT Tubes main system. Four plants have started to wilt. The heat index is currently at 108. I believe the plants are unable to to take in enough water due to their small root system. The same plants in the the Hydro Buckets are doing just fine in this heat. Not sure if the problem just due to lack of water or if the plants can't get air either. In any case, I added a air pump and air stone to the nutrient tank. Also increase the slope of the tubes to get more fresh water pass the roots. Checks the plants again that night and notice some were recovering from the heat.