The yellowish discolouration of tongue can occur due to-
Improper flossing of tongue.
I would suggest you to scrape your tongue daily with tongue scrapers.
Maintain oral hygiene
Discontinue the drugs administered if causing discolouration of tongue.
Apply topical diclofenac
gel on the affected area.
Avoid intake of spicy,allergic foods.
If symptoms persists,please do consult with your dentist
Hope this helps.