Why isn't my podcast pushing to my subscribers?

I recently launched a podcast. My first 3 episodes launched at once and were well received. When I published my fourth episode two weeks later, the next few days after it launched saw an undeniable significant rise in downloads/listens. I interpreted this as

1. people listened to the first episodes, enjoyed the show and then subscribed, then

2. when the fourth show went live it pushed and auto-downloaded on my subscribers devices.

When I launched my fifth show, there was no jump on the day when the show came out. If anything, downloads went down.

After looking at my own iPod and then talking with a few subscribers, the show is not pushing to their device. HOW CAN I FIX THIS??? I also noticed that the date on those two recent shows comes up as Dec.31, 2000, which is clearly wrong.

ANY ADVICE IS APPRECIATED!!!