Hi Gail. I am not sure what the condition was like before your highlights. When your hair is highlighted, the product removes pigment, but it can also remove your hair’s natural lipids for softness and shine, as well protein for its strength, especially if an inferior Decolorising or “Bleaching” powder is used. There are alot of professional brands that only remove colour and in fact add lipids and protein to the hair when highlighting. But you also get your cheap and nasty products.
The other thing that could’ve happened is that the stylist mixed Decoloriser with a strong volume of peroxide which can be damaging on the hair, but can also process too quickly, causing the hair to turn yellow, instead of slowly processing to a healthier pale yellow. The best products to use for damaged and dry highlighted hair is either Redken Extreme Shampoo R206 and Leave in Anti Snap R290. A great Silver Shampoo is from Matrix Total Results R105. The other alternative is Matrix Biolage Fortify Shampoo R125, Conditioner R135 and Leave in treatment R155. I would also suggest you let your stylist know how you feel, especially since you bought after care for your hair. I would suggest a few in salon treatments as well. Good luck