Okay, if it is below the 15th fret but NOT above, then your bridge (floating or not) is fine. What you need to do is loosen the truss rod.
This can usually be found under a plastic cover at the headstock end of the neck. Remove the cover, and you’ll see a large hex (six sided) screw. Your guitar should have come with a wrench for this screw.Turn this screw no more than 1/4 rotation looser (you will be moving the handle from the thick-string side towards the thin-string side.
Retune and play. If the problem is not solved, and this is IMPORTANT, wait 24 hours for the adjustment to settle into the wood, retune and check again.
This process can be repeated several times, but if you’ve done this 3 times and it’s still buzzing, take it to a shop. ALWAYS wait 24 hours after a truss rod adjustment (ESPECIALLY if you’re loosening it) before attempting to adjust it further. The wood needs time to settle and be checked again.
Remember, if you do this more than 3x (total of 3/4 of a screw rotation), and you’re not 100% sure of what you’re doing, take it to a guitar shop for a setup.
GOOD LUCK!