Some more info. The 2006 sale looks a little questionable to me. Are the seller and buyer related parties?

http://lajolla.whoboughtwhat.com/m/602031-1925–nautilus-street

It appears to be a bank-owned property.

http://www.sdlookup.com/Property-C41A0F03-1925_Nautilus_St_La_Jolla_CA_92037#8769