As was already stated by others, when you tune down, you must compensate for the lack of tension in the strings with heavier string guages or suffer the buzz and looseness. Just as a bass has heavier strings than a guitar, if you tune lower than standard pitch it can help to alter your string guages to maintain proper action and response from your particular instrument. Depending upon how low you go, this can also mean an alteration of the size of the cuts/grooves/slots in the nut and saddle so that the strings can ride and transfer sound properly without buzzing. If you fear toying with your stuff, bring it to someone you can trust to help you do the right job.