If you can see that wall near the pipes are moist and even wet, you probably have problem with leakages from the pipes.
The most likely reasons of this situation are below:
pipes became corroded
fittings of pipes are too loose
pipes are cracked because of freezing in the wintertime
Serious changes in pipes need a professional consultation from plumbers. Contact details to them you can find on this site: mdsplumbingandgas.co.uk.