Peanuts are fattier and less nutritious than sunflower seeds, and provoke a skin reaction in some mice.
Chocolate may be toxic to rodents in large amounts, although I have not seen the research. There is no need to feed chocolate to mice anyway – they would prefer sunflower seeds.
Anything you wouldn’t eat yourself because it might give you food poisoning – mice are susceptible to salmonella & other bacterial infections too!
Unwashed fruit/veg might carry pesticides etc. – wash or peel it first, unless it is organic. Washing/peeling will only remove surface residues, but it’s all you can do.