Hello everyone. I hope to learn a lot from all of you. I have been growing orchids for awhile in the house and last year, I had a 10'x12' greenhouse built. I use propane to heat the greenhouse and it is not vented to the outside. I also have a water butt to collect rainwater. As Ireland is a damp climate, the humidity combined with what the heater gives off, can keep the humidity from 60-90%. I have a fan running 24hours a day. We had a very dull summer and I did not take off my shade cloth until mid october. I was told that I had left it on a month too long. My query is that about a month to 6 weeks ago, I noticed that a lot of the leaves on my plants were going yellow. They were always the oldest leaves. Also quite a few plants that had flower buds, blasted. I had someone who is an orchid grower, come over and he said my setup was good. I am at a loss to know what caused this and he also could not explain it either. Was it the shade cloth being on to long, the propane, or could it have been water that went stagnant in the water butt? or could have this all been natural, exacerbated by the dull summer we had? I had a look at some of the pictures in the greenhouse thread, and I was very jealous of how nice and healthy the plants looked. Hopefully one day, mine will look just as nice.