Aw what a pretty bunny! Congrats on your new addition.
Holland Lops are born with raised ears. I've heard that in certain breeding lines, their ears can take up to as long as 6 months to fully lop.
Also some Holland Lops have what is called "ear control" throughout their lives - I think it has something to do with how their head/crown muscles develop. Some Holland Lops, even pure Holland's, retain the ability to raise up their ears when they want too. How much they keep their ears up I think really just depends on their genetics and muscle development.
You could try talking to the breeder. Ask what the normal age for her rabbit's ears to drop is. She may be breeding a line of Hollands that have ears that take a bit longer to fully lop.
I wouldn't worry about it too much. He may very well still be a pure Holland Lop and may just have wonky ears. But he's also still pretty young, so I'd say there is still a chance his ears will drop.