My 21 months old LO was sick and was prescribed antibiotic, which I later realized it caused yellow stain on her teeth. Any dentist to recommend so that I can bring her to? Can roughly share the charges?

You can go to the poly clinic. They have dentist there and subsized as well. However not all polyclinics have the service so it would be good for you to check which is the nearest one available to you. Also they only accept appointments.