If anyone is still looking for the answer, i've solved it like so:
$("#photos").on("hide",function(){
var leg=$('.videoPlayer').attr("src");
$('.videoPlayer').attr("src",leg);
});
Where #photos is the ID of the modal and .videoPlayer is the class of the iframe. Basically it refreshes the src attribute (and stops playing the video). So,
$('#myStopClickButton').click(function(){
$('.yvideo').each(function(){
var el_src = $(this).attr("src");
$(this).attr("src",el_src);
});
});
should do the trick.