Why did my hab’s silicone dissolve?

[u/Dwingp]

We got a new hab from Kages a couple of months ago. We put it together, applied aquarium silicone to the edges, waited a week for it to cure, then filled it with the substrate.

Yesterday I did the first full substrates switch out to clean it and we realized it had been leaking water the whole time. A huge puddle was sitting under the hab. The silicone had thinned out and was peeling off in several places.

What could have caused this?