They will flower but it will seem longer.You want to add 2700k bulbs in as soon as possible.You can use 6500k along with 2700k bulbs but you want more 2700k than 6500k in flower.The red/orange promotes blooming.
The 6500k spectrum will work, but your buds tend to not get as big. But at the same time, the way I understand it, they get more thc crystal growth on them. 2700k will still get you good thc crystals, but the buds on average will be bigger. Either way, the main thing that makes the plant push buds is the daylight cycle. 12/12 of either 6500k or 2700k or any combination thereof will get the job done. IMO 2700k is closest to what the plants get in nature, so thats what I give em.