It is normal, the plant has reached it's wilt point and no matter how much water is in the soil the plant cant take it up fast enough. You said the room does not go above 80, even at 79,80 deg. the plants can reach a wilt point. If you watch a plant outside in nature, often times in the heat of the day a plant will wilt because it just can't take up enough water but as the sun goes down and temps go down the plant springs back up because it is able to take up enough water. Hope this makes sense
If you notice it does not seem to be happening on the little seedlings since they don't have as much leaf mass yet and their root system is able to keep taking up enough water..
