Your HWH pump and solenoid manifold are under the coach near the entry step. The solenoids sometimes leak for various reasons and can be replaced. Each of your 3 hydraulic slideouts has a set of 2 opposing solenoids, one for IN and one for OUT. HWH used to recommend replacing both in a set, but advised others here more recently otherwise. You may also be low in fluid, but the threads below should provide quite a bit of insight.
You should review this thread on the Forum,
http://forum.bacrallies.com/m-1371831363/s-all/and http://forum.bacrallies.com/m-1383584861/s-5/highlight-Solenoids/#num5
then run a search for more threads here about slideout solenoids if you want more info. Calling HWH can also prove helpful. If you need it, I can provide you a copy of the solenoid reference in the '06 Monterey owners manual.
Supposedly there is a 1/4" nut driver on the tank fill cap that you can use to check the tightness of the nuts in the center of each solenoid. If one is obviously not particularly snug, that may be your culprit, but due to the soft brass inside, I wouldn't over muscle any tightening.
Joel