I would worry a little if it was built last October and was left to fill over winter,and hasn't yet become full. We live along the same lattitude roughly, the great lakes, more or less. I don't know your situtation but the type of soil there I am assumming is similar to around here. It only takes a spring thaw around here to max a ponds level out. I waited for my water level to come up more the first spring and it never did, that usually means, WYSIWYG, what you see is what you get. The loss of 3/4" a day is a little much this early in the year though too, so it does sound like you have a leak but I am basing this on conditions around here. Draining and fixing it is the only way I would attack it.
You mention shelves that were cut in, what were they cut into Rock? Shale? If they were cut into native/virgin material I can't imagine they would leak, also can't imagine any pond builder cutting into a material that would leak and not telling you he thought it would leak there. How deep are these shelves? Can you drain down to their level and fix them without completely draining your pond?
