Answer: That's a large greenhouse! Any time you have a large number of plants--especially the same type of plants--growing in one place, you're bound to have some pest problems.
If it is indeed botrytis blight--and this is a common disease, also known as gray mold--then you have provided the disease with perfect conditions; the fungus likes relatively low light levels and high humidity. Botrytis spores enter plant tissue through wounds--or even slight bruises--and aging leaves and petals.
There are a few things you can do to limit its spread. First of all, remove all affected plants. Try not to water from overhead, to keep leaves dry. Space plants as widely as possible, and prune as necessary so leaves don't touch neighboring plants. Increase air circulation by opening vents, using a fan, etc. Pick off aging flowers immediately. Unfortunately, few if any plants are immune to the disease, so your whole crop may be at risk.
I suggest you get a good reference book, such as "Greenhouse Gardener's Companion", by Shane Smith (Fulcrum, 1993). You will certainly encounter lots of challenges in your new venture, and this book should help you form a plan of action. If you are trying to start a commercial venture, I suggest you contact some of your colleagues, if possible, to inquire about pest management strategies. Your Cooperative Extension Service may also be able to help.
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