You need to have at least one relay in common with everyone you follow or you will not see their posts. 

You can go to each person’s profile check to see if you have a relay in common and add one if you don’t. 

Having too many relays will cause some apps to slow down. So be mindful of how many you add 

 That's not what happened. They were "removed" from my list. I had to click, follow, again. 

 Ohh what app(s) are you using? This is a bug a bunch of us are trying to track down and resolve. Also what relays did you remove? You can send this info via DM if you prefer. Thanks! 

 Fake news