So far my Four O'Clock seedling seem strong. They germinated in 4 days. I have been super diligent about keeping my humidity level and temperature in an appropriate range. I noticed that as the cotyledon leaves were unfurling out of the seed there was a white ball in one of the leaves of each seedling. It can be picked out and seems hard but you can squish it. When you squish it, it turns out to be a dry white powder. I have been scouring the Internet for every type of seedling/plant disease there is out there. It doesn't look like powdery mildew. I don't have any white on anything else. This isn't even on the plant. Once the leaf unfurls enough for me to grab the ball, I take it out. I accidentally squished one of the balls and the powder went on the seedling, which then I immediately removed the seedling out of fear that it is some type of disease. But so far the seedlings are growing really well and fast. I haven't allowed any of the seedlings to keep the ball out of fear it is a disease. I don't want to contaminate my entire greenhouse. I can't find anything about this online. I've asked a couple of gardening friends and they don't know what it is either. Has anyone ever seen anything like this before?