Sinking rear Suspension

I have a 2000 Discovery II that in the last two weeks has had a sinking rear suspension.  In the past it has corrected itself, but now will not raise the rear.   It seems to be the passinger side that fails initially and then the driver side follows suite.  I've tried to raise the suspension using the interior button, but now it does not correct itself and I can hear air escaping from the rear of the vehicle (both sides).  Temps have been averaging below 0 and I'm wondering if that may be a partial cause.  Any suggestions? 

 
Hi Firsty.
Rear airbags known to perish and start leaking.Easy to replace.
Regards
Marius

Cold weather will sometimes cause them to drop, I notice it here in Colorado, probably 3 times this winter.
You have 2 fuses and a relay, check them all first.
When the air leaks and you hear it, is it coming from the air bags or the pump unit on the frame under the drivers seat?

You have a leak in the air susp system. which may have damadged the air compressor! I would rec you look into a rear coil spring conversion, such as offered by atlantic brit. The repair is inexpensive and final!!

An SLS repair can be inexpensive, maybe not final but sure alot better ride on and off thge road.