Yikes! Started leaking after 3 weeks? You sure are patient. I would have leak tested it for 2 or 3 days max before starting to fill with sand/rock/saltwater/etc. But that would have just compounded the problem of a leak. Did you have it full of saltwater or just tap?
Well I wish you the best of luck with resealing it and setting it back up. I look forward to seeing it full of corals and fish one day.
