Can I use a silver shampoo every time I wash if it is 2x per week? I got a dark ash blond toner put in my hair and it was gorgeous with some subtle gray/silver highlights. By my second wash the gray has vanished and I am basically left with yellowish/brassy hair. It is faintly ash but my water is horrible (even when using a shower filter) and my hair seems to love to hang onto ugly yellow color.

I was told to use the shampoo every 2-3 washes: is this the same if I only wash twice per week or could I go ahead and use it each time? I tried to go every other wash using it but can't seem to go one wash without it turning brassy again. 

For reference it is the Matrix so silver shampoo. (Also should it be fading this quickly? I've never had color fade this suddenly.)

