Hi all I have a Parker duofold pearl and black fountain pen that I got about 15 yrs ago use it most days just purchased a matching rollerball second hand but there is a difference in the colour the roller ball is much whiter than my fountain pen which ihas gone like a yellowish colour to it any help why this is As happened is it just wear the rollerball is a 1996 and the fountain pen is 2006 thank you