thirty people? You mean thirty in search results, but how many actually listed in download window for that file?
One trick is to cancel the download & re-select from the search results. That sometimes spurts a download back into action. I've used that technique since I started using LW 6-7 years ago. It's not uncommon for download speeds to vary significantly as the uploader(s)' upload bandwidth speeds alternates between the people they are uploading to.

Downloads slowing to a halt can be due to a few reasons. At least one reason I don't have a clue why it happens. One reason is the person's upload bandwidth is busy as suggested above, so much so that in fact you 'might' have gone into a queue but LW has not yet responded by showing a message of busy host or similar message. I think LW 5 is less likely to show such messages, however I have not yet used LW 5 for very many heavy sessions.

One reason might be you are using most of your bandwidth for other downloads.

I've watched my uploads for considerable time. Often one person steals much of the upload bandwidth .. perhaps 2/3. The other uploaders might suffer, even drop to zero for a period of time & occasionally drop out of the upload window. Not sure why this happens, it's something that should be looked at by the devs.

So ... cancel & re-select from search results if you have search results up, and also re-search or Control-click the search tab & choose Get More Results. Fresh hosts can sometimes also help get a download re-activated/re-energised.