headlight lense mysterious "star" shape cracks

[smitsz1]

I own a 2000 m roadster. The other day I noticed the pass. side low beam headlight was out. (the bmw dealer has replaced both pass. and driver side low beams in the past.) As I inspected the "glass" lens -(I was looking straight into the headlight lens) and located under the plastic cover I noticed on both sides on the low beams that their is a "star" shape type of crack (one on each lens located almost in the identicle spot) when looking into the lens where the "star crack" is located it appears, to be a amber/yellow color or burnt color? any info graetly appreciated ***Low beam bulbs are sylvania 9006 51 watts****