Certain pages on my site, primarily threads, are failing to load. When looking at my control panel for my host I've noticed that I'm allowed 150mb of memory usage, while my forum is using 380mb. My 5 year old forum has approximately 2000 members, but rarely are there more than 30 on the forum at any time - so I'm definitely using a small amount of bandwidth. My database is 250mb and overall size of forum with attachments is 885mb. We have 5000 topics/62,000 posts. Note that I don't have any mods other than an image resizer.
My question is what exactly is causing the excessive memory usage? Would pruning unnecessary/unused accounts, old posts, attachments help? Is 380mb really too much for a forum my size? I tried searching for info, but haven't found any info relevant to my issue. I just want to get the forum running again without having to pay for an upgrade to a "dedicated" account.
Edit: Attempting to poke around in the admin panel of the forum to check settings and prune users, memory spiked to about 460mb. I can't really even use the forum at all right now without 502 errors.