I doubt they used silicone or Lexel at the factory.
Typically that is 2300MHRV made by Geocel.
Here is the Literature Link
on Their products.
Sometimes the 2300MHRV is tough to find but the ProflexRV is consumer based and often available.
Lexel is a good choice for touch up work but I've never seen reference to it being used at the factory. I use it when I don't have ProFlex RV available.
In any case DO NOT use silicone sealants on a R/V. Nothing will ever stick to it again including additional silicone.
I would think cleaning what you have could be accomplished with any good mildew cleaner or LA Totally Awesome. Be careful of bleach based cleaners on color/paint.