We are in First month of summer.why my girls are pre flowering?

Your plants "know" what they are doing. Better to start early and finish early, before Fall rains begin!

if your sun is setting at 720pm, it's clearly not a long day. this is biology of the plant and nothing else. It flowered because it got a long enough uninterrupted dark cycle. The required length for this flip to bloom varies by seed.

Depending on where you live in the northern hemisphere, flowering starts July 15-Aug15. But, I see you were at 18 hours of light in earlier weeks. So I assume you used a lamp part time to get to 18 hours. When you step down fast from 18 hours to 14, it will trigger flowering. I see this happening in week 11 on your grow. The light green new growth is a sign. How it goes from here can vary. Some indica can settle into flowering and keep going- this is your best outcome. Sativa stems to reflower and you will get foxtailing on your buds and end in October. In either case, going from inside to outside has to be timed exactly with 3 minute reductions per day. It’s a pain. Check out my light deprivation grow- you can do this and get great plants. Best of luck with your grow.