Rate lock expired.. rates much lower now.

[Eric P.]

We're in the middle of purchasing our first rental.  The process is taking longer than expected which is okay.  Our rate lock is expiring, and our mortgage broker sent us documents to sign to re-lock the rate.  We did the original rate lock when the 10 year yield was at like 3.25 and the rate was 6.3% now the 10 year yield is 2.95 and I'd have to imagine rates are 6% if not lower.  

I don't care too much since the mortgage is only $80,000..  I don't think my lender is looking to charge me a fee to relock, but am I correct in assuming we can't get a lower rate?  Is it worth asking if we can split the difference?