Based on the types of food mentioned, I would suspect that the Halakhah differs for each one. Regarding bulk candy specifically, the Star K says:
Bulk & Repacked Candies: Today, a more economical way of purchasing favorite sweet treats is at the bulk food section of your
supermarket, or in convenient repackaged cellophane bags. Often when
purchasing candies in bulk, the individual candies remain wrapped in
their foil or cellophane units and can be identified as a Kosher
candy. Some candies are loose and unwrapped. Unless the store has
Kosher supervision, once the individual units leave the original
packaging, the original Hechsher is no longer effective.
So regarding candy, they are taking a strict position, saying: once the individual units leave the original packaging, the original Hechsher is no longer effective.
I am guessing that you are wondering if there is any halakhah similar to the application of "rov" regarding a piece of meat. In today's food manufacturing and commercial environment, I don't think you can make any assumptions about what the contents of the bulk containers are from day to day. So, for any item requiring, I would say that you always have to check the original packaging of what's in the bin, and possibly, if following the Star K's advice, maybe even that is not good enough.
Of course, this is only a lay opinion, and you need to speak to your Rav to get psak halakhah.