Yellow Silicone? Thats not right…

[yellowworld]

Hey guys, so i think i might have a problem, I get back home from work and I'm starting to notice that some of the silicone in both my tank and my sump are starting to turn yellow, its both the factory silicone as well as the silicone that i did. so i emptied the tank and sump and gave them both a good scrub to see what was up but it didn't come out at all, there is no algae on the glass, there was a few small spots of a dark brown algae on the yellowed out silicone but thats all! so now I'm starting to get conceded I've never seen this before especially seeing that its both the factory and aftermarket silicone, ill get a few pictures up too

any one have any suggestions?