Fungus: 50/50 mix of hydrogen peroxide and ammonia, will remove fungus from a glass lens. rinse in water and then wash the lens with dish washing soap, and rinse in cold water,or distilled water. Not sure how it will effect a plastic lens.
If the fungus is really bad, I have heard use Pond's Hand Creme. Although I have not tried it yet.
Corrosion can be removed with plain old vinegar. Let it sit for day.
Vinegar is a natural acid.
If all of this does not work...go here and ask...
good luck !!