Mold in bathroom cupboard under sink and in adjacent washer dryer compartment

[sonofcy]

We have a 2018 Montana 3811MS bought Sep 12 and just found significant amounts of mould under the bathroom sink compartment and in the dryer compartment. In the case of the under bathroom sink area, it is on the outside wall therefore cold. It even had a small blob of liquid water. My wife noticed a pipe that we believe is the plumbing vent for the bathroom sink. We also noticed that the washer drains into this drain as well. Our theory is the vent is allowing warm moist air into a cold area which will, of course, cause condensation.
My question is directed to other owners of this model. Have they checked for mould, if so do they have any and if not what did you do to prevent it? My wife thinks we need to turn on the power vent whenever we are using the washing machine.

We forgot to take a picture of the area under the bathroom sink but did get one of the dryer compartment. (Rotate pic right)

[sonofcy]

We just discovered the water is actually coming in from above. Tomorrow I will get on the roof and attempt to seal the leak. It is near the edge/corner of one of the slide outs so a corner or edge is involved or even the mounts for the topper. I would just delete the post but don't know how.

[ctbruce]

Leave it as it may help someone else in the future.

Also, take a picture of the leaking area. From your description it sounds like the leak was caused by a slide topper installation. Do you know if butyl tape was used?

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[sonofcy]

Too late for a picture my wife cleaned all the mould off before I thought of it. We did post a picture of the mould in the dryer cabinet. I too suspect the topper mount, but can't get a look at it until it stops raining.