Hi!
The main problem with your script is that you are not using the “event receive draw hud” node for building3 so you’re basically not telling the hud to actually draw anything. That’s why the text is only showing when you hover over building1. Anyway, the whole script is a bit of a mess (no offence, please. I’ve been there too! 
), so let’s just try to clear things up a little bit.
Since you can use only one Receive Draw HUD event, the only way to write different pieces of text is using a string variable that you will set from whatever building blueprint you are hovering. In short, use the boolean to tell the hud whether to draw or not, and use the string variable to tell what to draw.
Also, I noticed that the script in building1 and building3 are exactly the same, so the way to go would be to create a “building” class with a public string variable that you can set per instance in the editor. This way you can use the same object with a different setup for every single building in your project, whitout having to rewrite the same piece of code over and over again. Be lazy! 
A different approach -and probably the one I would choose- would be using a 3dwidget attached to the building instead of the HUD. Is there any reason why you need/want to use the HUD?
If that was greek to you, don’t worry! I don’t have enough time to provide any screenshot and detailed step by step process right now, but let me know which approach you prefer and I’ll get back with a little guide asap.
Cheers!