There's one thing I can really think of which may be causing this problem: a really crazy welcome system (e.g. fireworks, long chat welcome messages, etc, whenever someone joins) -- if a really exaggerated event happens whenever a new person enters the server, then the source of your problem is quite obvious. For the mean time, trying a higher RAM plan for the day and checking if it sorts things out might be a good idea, if not, I would recommend making a support ticket, so that the Minehut development team are aware of the issue, and, therefore, can attempt to mitigate it.