So after the system was switched back, the lettuce has begun to re-hydrate and is looking good. The water is still a little high in pH, so the pH down was used. The lighting is still on for about 18 hours and with the increase in water the lettuce should continue to grow well.
Your plants have already rebounded after your wilting disaster. Your system was able to successfully bring back the lettuce which says a lot about the design and overall product. Did any of the plants have to be removed and reseeded?