Discoloration of Acrylic combs

Hi,

I have white acrylic combs on my Seydel Silvers but have noticed it discolored to yellowish. Yes, I do clean my harps and even soak them in water since they have stainless steel reeds. I tongue block so I'm thinking it might be my saliva? What seems to be the cause and what is the remedy besides changing the combs. At this point in time I don't think it is wise for me to buy extra combs.

Thank you.

Ricardo