Is my Cat lacking nutrition??

[k21573n]

LAst night I was just chilin with my cat, andI noticed that his tail has become slightly ringed. He is all grey in color, yet his tail now was black rings around it. I don't think It's normal. He about 3 ot 4 years old so its not like he's a kitten and just growing up. Im getting a bit worried, because I am scared he's going to die on me. Does anyone know why this might be happening??
Could it be stress? Or not enough water? Or not eating enough? Im so lost...

 

[gailc]

One of my cats -her fur changes color with the fall and winter weather coming. She become much more orangish in color-she's 10 and has always done this. Perhaps its similar with your cat. Sometimes with her tail too it will become more bushy and then in spring becomes less bushy!! I don't ever recall hearing of any medical condition to cause color changes specially in one area.