to have different rules for dd1 and dd2?

[DorothyL]

Dd1 is 14, dd2 is 12.
Both have smartphones. Dd1 is very sensible and self-controlled about using it which is why I haven't imposed any particular rules. Dd2, however, gets irritable the more she uses it, it affects her mood, she's easily distracted, which is why I want to impose stricter rules about phone access. Dd2 complains this is the height of unfairness - is it?

The way I do it with DS is to define rules according to his maturity and the trust I have in him. If I can trust him, it's fine. If I can't then the rules are enforced.

I think that system can work well with your DDs.