Not all of my items are showing up

[Pi man]

I use MediaFly to subscribe to many podcasts and get them into one RSS
feed. However I like the RssPlayer app on the iphone, not MediaFly's
app. The app can only use certain RSSs and the direct RSS for
MediaFly does not work, so I have been using FeedBurner, and it has
worked well. I have noticed that FeedBurner is not grabbing all of
the items. A lot of the time I get many episodes for different shows
at the same time, and FeedBurner only gets some of these. How can I
fix this, also I cannot edit any settings on the MediaFly RSS side as
I do not own the site. Any help is appreciated,
Thank you,
Michael