Hello,
As for now, to remove space between videos in mobile view, please add following given CSS in Additional CSS section by going to Admin Panel > Appearance > Customize > Additional CSS
@media screen and (max-width: 768px){
.wp-block-embed iframe{
height: 410px;
}
}
@media screen and (max-width: 668px){
.wp-block-embed iframe{
height: 355px;
}
}
@media screen and (max-width: 568px){
.wp-block-embed iframe{
height: 310px;
}
}
@media screen and (max-width: 468px){
.wp-block-embed iframe{
height: 255px;
}
}
@media screen and (max-width: 368px){
.wp-block-embed iframe{
height: 215px;
}
}
Hope this helps.
Thank you.