I've just brewed my first all-grain beer and I'm excited to share my experience. I used a DIY mash tun made from a 20-gallon food-grade bucket. The recipe was a simple pale ale, and I followed the instructions to the letter. However, after the mash, I noticed that the wort was slightly under-pitched. I've checked the thermometer and the temperature was within the recommended range. Has anyone else had this issue with a DIY mash tun? What could be the cause and how can I avoid it in the future?