Howdy Bobby sue and welcome to the forum.
I had a similar experience on my last grow, but it was related to trying to adjust the pH directly in the reservoir and adding too much, too cold water into the tank. The grow was running during the summer months and I was making up (pH'ing the water) a day or two ahead of the feed or midweek watering. Because of the problems with algae growth in a warm reservoir, I was chilling two gallons of water in the refrigerator over night for each reservoir. Most refrigerators run around 40 degrees F. The combination of these two things shocked and quickly wilted my plants! I panicked (seemed like a proper reaction at the time., LOL), but did the right thing, I drained and re filled the reservoir with new pH'ed and warmer water. Now I use only one gallon of cold in the reservoir and ONLY if the ambient temperatures are in the 90's or above. Also the chilled water is poured in the reservoir last. I use frozen ice bottles to keep the temperature down, but I try to never allow the water temperatures to drop below 63 degrees F.
Good luck with Your grow.