Even if the symptom “Premature end of script headers” is the same, the problem most likely lies somewhere else. Please, post on the forums enough details for people to help out.
DreamHost has quite a few articles that describe what you can do to make your sites faster and more responsive. Some of the techniques and tools suggested for WordPress here https://help.dreamhost.com/hc/en-us/articles/215300867-General-WordPress-optimization-techniques can be applied to other PHP software.
When you write on the forums, and when you file support tickets, the more details you share the more chances you have to receive useful comments. Here for example, specify if your site is running on VPS or shared hosting (from the forums we can’t guess what kind of product you’re using). Also, it helps to know what software you’re running on that server (is there only one wiki? one mysql server? how many databases? PHP/python/ruby/java?) Instead of saying ‘mysql is slow’ give precise details and metrics, like: “with 20 active users on my site I notice that pages take an average of 25 seconds to load as measured by pingdom.” or something similar, something we can work with.
Otherwise your message will likely be ignored on the forums because it requires too much work for people to respond. DreamHost tech support will still respond, but will ask you more questions which will just make the ticket resolution take longer. Give more details in advance, save yourself time.