Don't sweat it. Your work has been so well drafted, and it's perfectly normal for you to not fulfill those requests in a time span. It also depended on the complexity of the drawing, so there's that! Trust me, it's not your fault at all.
These are only my 2 cents on this and don't feel bad if you won't deliver all requests. You are doing this voluntarily. If you are able to fulfill a request it's a gift to the respective person, but if not, nothing is lost. So even if I overlooked requesting something here I still wanna thank you for this thread. Watching the other requests you did was still amazing!