Thank you everyone, i was very worried about DD2 as DD1 talks quite a bit, SIL's son is in speech therapy as his older sister basically spoke for him for the first couple of years of his life.
My younger brothers are close in age and the 2nd child was also a little slower as the older child took control, i have been trying to teach DD1 she's NOT to talk over the top of DD2 and she's not to end her sentences.

I talk a lot so i guess the girls have already picked up that they need to chat a lot themselves to stay ahead..

Beckoes - DD1 has on more than 1 occasion used the S & F words in context so i know what you mean.
Word of the day is a great idea too, i was quizzing DD1 on words while we were driving, got her to say things like utility, greensborough, our home town and things like that.. cheeky little turd would huff after each one like come on mum.. REALLY... lol