Dishwasher not cleaning top rack

Hello,
we have a dishwasher bought in 2007, and the dishes on the top rack doesn’t seem to be cleaned. The glasses are not shining as before.
I already found a forum on that subject but it concerns another model number from whirlpool, I was wondering if it’s the same explanation for my GU2455, with the same part diagram as the DUC600?
Thanks for your help
Peavey35