I really am not sure what your host log is trying to show. Your definately going to have multiple processes of a script running on a server simply because if you have 100 people viewing 100 different photos at the same time there are going to be multiple processes going on. There is nothing wrong with that.
Photopost runs on bare bones sites to high end servers. You would definately need to look at where your load is being generated. You might also want to read the performance thread in the DOCUMENATION and FAQ forums on things you might want to turn off to avoid some overhead. If you also run a NIX server there is a load balance feature in global admin options you can set to a number between 0 and 10 usually about 6 or 7 and it will shut your photopost down to new visitors until the load drops telling them the site is too busy now.
It is all about balancing features with your server. If your load is coming from lots of people viewing the site which ups the load with more processes all you can do is upgrade hosting to help.
PhotoPost Performance FAQ