Hi, Larry...
Via this link
www.luftwaffe-experten.org/stammkennzeichen.htm, I noted the following. Please note, they are listed under 'civil' style alphabetic codes on the site with no '+' (national marking or Red Cross). However, there seem to be some details matching Seenotflug machines which you may wish to double check for yourself. Sources for the information below are logged against each entry on the site. Hope they may be useful to you.
D-A+DIU - He59D-1, W.Nr 1819, Stkz DA+MR, KGrzbV.108
D-A+LYO - Seenotstaffel 1
D-A+NYI - He59N, W.Nr 1628, Seenotflugkommando 3
D-A+HIK - He59N, W.Nr 1522, Stkz DS+KA, Seenotflugkommando 2
Sorry, nothing at all on D-A+QUV
The site neither confirms nor denies the machines being white painted 'Sanitäts' machines.
Kindest regards...
Paul