Can you provide more details? At what point are you finding the green stuff? You said you are using it for a week. Are you keeping the fermented feed refrigerated at this time or are you keeping it in the fermentation jar/bucket for that long?
To me (from what I can gather so far), it sounds like you are making more than you need. You shouldn't be using the same batch for more than a few days, and I keep mine refrigerated after it is done fermenting. So for example, make a smaller batch that your flock will consume within about 3 days (the amount of time it takes to make a new batch), so that you constantly have a new supply ready. That way, it won't go bad. There should not be anything green and I would dispose of feed that does have that because it could be mold.