If your feedback says "research from broader sources needed"
This is probably because you haven't used enough sources or your sources are not diverse enough.
Answer
What does this mean?
It is likely that you aren't referencing enough sources of research in your work. Simply using different areas from two or three books is not enough evidence in your essay. A wide range of academic sources is more appropriate and allows you to pull ideas from different points of view and experiences.
What should you do?
Go beyond what is given to you in your reading list - try to find academic pieces of work that are relevant to your assignments. 
The DMU catalogue, DMU library and google scholar are just some examples of places to find relevant research when trying to diversify your reference list with a range of sources.
When researching for relevant sources of work, ensure the work you're using is academic. Try to avoid referencing websites and other unreliable sources in your academic work - see the "To use or not to use" tutorial to understand how to choose reliable sources for your work.