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Some lenders offer a one time float down...that lets you drop it once if they go down.
If they didn't tell you ahead of time that you have that option then you don't.
Get a copy of your loan application if you don't have it already. One of the page you have signed should be about the rate options. If you haven't specifically asked to lock your rate they probably just went with the default and that's maybe the floating.
If you are on floating term then you can still lock yor rate.
Laz