How many letters of recommendation did everyone send in? Did you just send in two, or did you send additional ones?

2 should be fine. Try to get them from your work supervisor (who is able to evaluate your non-academic skills such as time management skills and such) and the other from one of your professors or someone from your undergraduate faculty who can evaluate your academic skills,and can put in a good word regarding your academics i.e. your improvement over the years etc.. etc.. Those are 2 examples, you can get them from other people as well, but make sure they are professionals (don't get one from your T.A or anyone like that)
Goodluck!