CRI is a function, very largely, of how near to full spectrum any light source is, not that even very high CRI fluorescents, used specifically for colour matching in print works and the like, are anything like full spectrum.
Perhaps I could get some missing lines in the LED spectrums here by closing the slit on my spectroscope right down, but the lamps here are SO close to full spectrum that they appear to be full. Looking online, quickly, I can't find a CRI quoted for lamps on LED Hut website. Also take a look at Wikipedia to see how the two types of "white" LED work, and their spectra. A CRI down in the mid 80's seems remarkably unlikely for phosphor based LED lamps.
Degredation of plastics is MOSTLY down to UV and although standard glazing is a VERY good UV absorber, it isn't 100%. UV causes colours to fade and plastics to become brittle. Plasticised plastics will forever leach plasticiser as plasticisers are mostly (but not exclusively) oily liquids, so they simply diffuse out. Diffusion rate increases with increasing temperature.
It WILL be online somewhere - try to find an archivists' forum and ask there even, but I am not sure what the brown discolouration is, as it has been unimportant in the areas with the plastics industies that i have worked in, but I would tend to bet on some kind of diffusion/surface degredation combining with general atmospheric muck, or even reacting with packaging materials, or mobile components within the pacakging materials (cardborad generally smells reasonably strongly, so will be full of volatile/mobile gubbins). Perhaps the best way to keep things like computers would be inside a thick, sealed, old-fashioned polyethylene bag?