From what I've read lemons are bad for beardies. That being said, what your dubias eat will go into your dragons, but don't take my word for it...
I've had a colony myself before, and I've mainly fed them orange.
You know how you can get free oranges?
Go to a hotel that serves breakfast or look up hotels that do serve fruits near your area. Pop in there during breakfast hours and grab yourself one or two. That's what I did.
You shouldn't be feeding directly from your breeding colony anyways.
But yea, my colonies won't eat lemons, limes, or parsley. One time I put a carrot and potato slice in there, with a piece of parsley laid directly on the potato. They literally ate around the parsley. They carved out a parsley-shaped potato slice. :lol: