Upload & Sell: Off
More than likely it is a combination of issues, however, mainly, it is an issue, IMO, of fabric/dye florescence:
We used to photograph a lot of fabric, years ago, particularly dyed woolens/yarns, etc., and ran into the problem often.
"Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation. However, when the absorbed electromagnetic radiation is intense, it is possible for one electron to absorb two photons; this two-photon absorption can lead to emission of radiation having a shorter wavelength than the absorbed radiation. The emitted radiation may also be of the same wavelength as the absorbed radiation, termed "resonance fluorescence".
"The most striking examples of fluorescence occur when the absorbed radiation is in the ultraviolet region of the spectrum, and thus invisible to the human eye, and the emitted light is in the visible region."
"Fluorescence has many practical applications, including mineralogy, gemology, chemical sensors (fluorescence spectroscopy), fluorescent labelling, dyes, biological detectors, and, most commonly, fluorescent lamps."
This is a phenomenon not commonly known to most photographers who often are quick to judge perceived lens inadequacies, rather than understanding this issue and correcting exposure, using filters, changing light source, etc.
In the end, the result is not unlike other wave length distortions such as mirage....
The article does not go into depth about this issue, but is a beginning entry point.
Very closely related - OBA's are also contributing factors. Jmcfadden is correct: http://en.wikipedia.org/wiki/Optical_brightener
"Optical brighteners, optical brightening agents (OBAs), fluorescent brightening agents (FBAs) or fluorescent whitening agents (FWAs) are dyes that absorb light in the ultraviolet and violet region (usually 340-370 nm) of the electromagnetic spectrum, and re-emit light in the blue region (typically 420-470 nm). Fluorescent activity is a short term or rapid emission response, unlike phosphorescence, which is a delayed emission. These additives are often used to enhance the appearance of color of fabric and paper, causing a "whitening" effect, making materials look less yellow by increasing the overall amount of blue light reflected."