I don't know anything about that company/pattern, but I would stop using the pieces that are crazed.

I like Wedgewood, esp. the celadon color. I had an elderly friend who had a most exquisite collection of the blue color. However, her alcoholic son convinced her to sell it for mere pennies... I notified her other sons when I discovered this fact. But by then, the collection, and other items were gone. We never did find out who bought them.

Pottery will craze...vitrified ware, be it stone ware or porcelain won't.
I know some say that there may be germs that are harbored in thec razing, but I don't know of anyone who ever got sick from drinking tea out of a stained cup. That's one of the reasons for the popularity of the British Brown Betty....doesn't show tea stains.
Tea will stain earthenware...If you don't like the stains, bleach them out and don't use the cups for tea....or coffee.
Linda C