It's most likely the air legs , it's the exposed rolled edge of the bag the tends to perish and weep , taking the car to full height exposes a different area and in some cases it either stops them from sagging or greatly increases how long it takes to sag .
You can try spraying soapy at them but in sure they have a ally shield around them so it's difficult to get them and ideally you need to be on a drive on ramp to get at it .
I do lots of range rovers , Discoverys and that ....it's mostly the bags but have seen the feed pipe to the leg chaffed through or the corner valve leaking air back to the resvoir .
