Your daughter is 7years old, in this age her permanent teeth are coming out in mouth. Teething or tooth eruption is reason for black gums which is normal in this age. Nutritional deficiency or Poor oral hygiene are other possible reasons for black gums. It can be hereditary also in some cases. Visit a dentist for oral check up to rule out any other reason and keep good oral hygiene and nutritional diet for her.

Usually Dark pigmented gums are commonly seen in dark complexion people, this is normal, to this if she has mouth breathing habbit, gums vl become more dark, we can change the colour with lasers but she is still young let her grow v can take care,mean while Pl check for mouth breathing habbit u dont hv to worry.

Brushing and flossing your teeth properly, twice or three times a day Gargling with a good mouthwash or some warm salt water twice each day Quitting unhealthy practices like smoking and chewing tobacco Following a diet that is high in vitamins, minerals and other essential nutrients Practicing stress reduction techniques like yoga, meditation and deep breathing Undergoing regular cleanups at the dentist..