Yorkshire Tea

Had your tea bags for years,have recently(last 6 months)been finding residue on the surface of the cups.

Have had to use a tea strainer to try to stop this residue getting into the cups,i am not talking about a lot of residue but it is floating on the surface and i have to use a tea spoon to remove it,The tea bags are placed into a tea caddy and well shaken before use,have done this for years,is the tea now produced much finer or are the bags thinner and powder is seeping through.I will continue at present to use your tea bags love your tea.pete