Yoga and stretching are not known to help in increasing height and are unlikely to result in any meaningful increase in height. Chances are slim for further increase in height, but could still increase till 21 years of age, given growth plates aren't fused.
Next Steps
Consult an Endocrinologist / General Physician for workup of possible causes of restricted height.
Health Tips
Avoid using unproven methods of increasing height from internet and social media, as this could delay the actual management.