Thanks again Dubbaman, that makes me feel better. I've had bud rot before, but each time I could have prevented it in spite of the average RH. That is to say, once during another grow I could have prevented the colas from other plants from falling over and leaning on this big fat cola of another plant, bringing about bud rot. During another grow I had to take off for about 5 days without notice and had no one to water my plants. So, I watered the crap out of them and then pretty much closed the door. The plants had enough water to last them, but the closet had mildew on the ceiling and walls, and some of the plants had mold. If I don't screw up like that then I think I should be ok as is. I might look into a small hehumidifier though.
The 21 degrees was in celsius. CubeCap started off in celsius, so I continued with it. The low temperature is about 71 degrees. I did notice that the RH had gone up to 87% last night and with bod rot on my mind I started to get concerned. Hopefully it doesn't go that high very often. I came home tonight and opened the closet door for about 5 minutes. Plus, every night before going to bed I open the door so it will be open when the light comes on.
Andy, thanks for the advice. I saw some for $11.00 that simply absorb the moisture from the air, and you don't plug it in. So, get an electric one that you need to empty? CubeCap said I could get one for about $50.00. I hope he's right, because if he's not, I might not be able to buy one now.
The plants look good and none of them have mold as of yet. The one that's the ripest is the most vulnerable, yet no mold for the moment. I think they'll be ok, I hope.