Degenerating video quality

[rav96]

i think that there must be a problem with the layer!
thats why its spreading

did you spill anything on it?
colud be due to solvation in the layer?
does your DVD player get really hot if used for ages coz heat can degrade DVDs

ive also heard that there is a type of fungus which affects CD that is transparent to the naked eye and it corrode the data.

not sure if it affects DVD though...