the short answer is i don't know. but you were smart to listen to your plants and if they don't like the heat then cooling was necessary. i'd think a temperature swing from day to night could be 15-20 degrees difference without harm (again i'm not sure ... just surmising) but it seems like a lot of temperature swings throughout the day would be unnatural (but then again so is 24 hours of daylight)... hmmm good question think i'll stick with my orginal answer ... i don't know.. sorry