There is calculus deposits between teeth
Which itself is cause of gum recession
And gap will keep on increasing with age( though very slow) with calculus
Get the deposits cleaned(after cleaning these deposits you will see spaces which were occupied by these deposits, and will feel more space)
Next Steps
Consult dentist , get teeth cleaned
Then many options available for diastema closure
Health Tips
Do rinses after every meal
Massage gums in direction from gums towards teeth