Two issues, one with design, the other with your algorithm. Design-wise, I'm no expert but you need to make better use of space. The grey boxes are spaced too

Two issues, one with design, the other with your algorithm. Design-wise, I'm no expert but you need to make better use of space. The grey boxes are spaced too closely together, and the text in each box is too close to the border. The uneven vertical dimensions of each group of boxes is subtly disturbing and stops me taking in the content. Your colour palette is a bit odd too. Algorithmically, you're relying too much on your "authority" rankings. The result is that the top of your site is over-stuffed with HN links. My solution would be to assign an "exhaustion" parameter to each source. Each time your algorithm picks the next article to show, it increments the exhaustion parameter for that source. Then you can just subtract the exhaustion parameter from the authority score in order to give other sources a chance for the remaining space on the page. Tweak the weighting of the parameter to taste.