Thread:Extension talk:SphinxSearch/search is sometimes case sensitive

My site it thepetwiki.com If I search for 'adopting a feral dog' it doesn't bring back the article page but 'Adopting a Feral Dog' does. However both 'our natural pets' and 'Our Natural Pets' brings back results. Why would this be so? The sphinx is running. Is the default Mediawiki search engine conflicting with it? Any ideas? Thanks