TMI toddler poop question

Annie

The last few days my one year old has been having really wet/explosive/yellow poops. This isn’t average for him at all. Usually he will poop like brown/orangish whole pieces (like normal adult). But this has been happening for a few days. He also has been having a runny nose. Everything is the same except for drinking thawed expressed milk that has been previously frozen for him. Has anyone experienced this before? Any ideas?