If you bought the Dragons Charm in bud it could be bud blast caused by change in environment at your house from the store or from the time it spent outside, changes in temp caused one of mine to get bud blast and I lost all but two blooms, my Phals also seem to periodically lose there oldest leaves they turn yellow and drop, I would guess so long as the rest of the plant is healthy it shouldnt be too much of a worry but someone more experienced with both can tell you more, just thought id try tell you what has happened with mine.