Do you prefer coffee or tea?
My little seedlings definitely prefer tea - chamomile tea!
Let me explain ...
Warm, wet, humid conditions as are often found in a greenhouse can cause "damping off". This is fungal condition that spreads quickly and kills tiny seedlings - they sort of just turn to slime and disappear. It's very discouraging to watch seedlings grow & thrive and then suddenly die. Keeping the greenhouse cooler & drier will help, but that slows down seed germination & growth. Plants can also be sprayed with a fungicide.
But I prefer watering with chamomile tea. Apparently it has anti-fungal properties and prevents the disease from starting. I've been using it for years now, and rarely lose any seedlings to damping off. An easy, inexpensive, safe solution to a serious problem.