Thank you for your query on Healthcare Magic.
Your twins have tongue coating because of a decreased oral intake for past few days.Oral thrush
also to be looked for.
The sore on the tongue may be due to an aphthous ulcer which is seen after a viral illness.
Hand foot mouth disease presents with ulcers in oral cavity and with skin lesions on both hands and feet.
Maintain their oral hygiene
Give plenty of water and oral fluids to drink.
Consult the pediatrician
for physical examination and specific treatment.
Hope I have answered your query.