It sounds like something's going on with the kids. Is it possible for you guys to see a family counselor together or maybe even your pastor? Have you ever read Gary Chapman's 5 Love Languages for Children? It's be worth doing. Might help you understand the kids and give you ideas on dealing with each one. It may just be growth problems but I would try to talk with them seriously one-on-one, starting with the 8 year old. Sounds like something's on her mind. Has anything changed over the past year? I'm sure you're praying. I doubt there are any easy answers, even though someone might tell you that. It's tough that you're doing this alone, but lots of women have to and the Lord is certainly with you.