Our home got a talk deck at back of the house, the backyard has some slope. During rain, it became muddy on the ground (under the deck), also due to the drainage pipe was not smooth (might be blocked/narrowed somewhere under ground), big rain will cause water to build up underneath the deck around the foundation..

I ordered 8 yards of 1 inch gravel and put them under the deck, the deck size is about 370 sq feet. I think I ordered a lot more than what actually needed, the thickness is roughly above 4 inches and even about 7 inches at one side.
To stop the water to sink into the ground, I put a layer of plastic underneath the gravels.

Now someone told me this is a wrong way, and this will cause damage to the foundation, since water will build up there under the gravels and will not be dried by sun.

I want to know whether what I did was really wrong or not; if wrong, what should I do now?

Thank you very much for your answer.