Hi Kevin
Sounds to me like you need to get someone to show you how to tune your guitar correctly - the tuners are not there to adjust your action up and down - they are to enable you to set the strings at the correct pitch.
A strat bridge is usually "floating" This means that it is held in one position due to a balance of the string tension and some springs that are fitted inside the guitar. At the normal pitch the height of the strings should be correct.
If the strings are too slack, the bridge will sit flat on the body of the guitar (which in itself OK - some players prefer this) but the action (adjusted at the saddles) will need to be set with this in mind. It may be too low otherwise.
Conversely if the strings are too tight, the bridge will be pulled foreward and up (raising the action a bit in the process).
Do this too much and there is a good chance that something is going to break - with luck just a string.
Take it back to the shop and get them to show you how it all works.
Some guitars set up with very low actions do buzz sometimes - usually, if this doesn`t sound through the amp, this is considered OK.
Apologies if I`ve misread your level of knowledge on this - it can be difficult to tell from posts, where people are at with their playing
Regards
Will