Can flower end early?

I have learned that each plant has its own growth and maturity schedule, and that each can grow quite differently. The best advice I can give you when growing multiple plants at the same time is to defer opinion and desire to fact based evidence. The absolute best way to determine if a plant is ready for harvest is by looking at their trichomes under a small microscope or jewelers magnifying tool. You can find both on Amazon at reasonable prices. Harvest should be done when your trichomes have a milky or cloudy appearance, with some amber trichomes spread throughout your buds. 75% milky to 25% or less amber. The more amber colored trichomes the less potent your bud will be. It also depends on which effects you’re trying to achieve with your bud. If you want more of a heady, euphoric type of high, you don’t want too many amber colored trichomes. It really comes down to what you’re looking for in the end. Trust your trichomes, and do the research needed to determine which is best for you. I hope this helps. Good luck with whatever you decide.

This plant is far from the finish. But with seeds you have different phenos so plants are different

You could grow 6 of the same strain from seed and you would be lucky if all 6 finished at the same time. I use a product called ripen when I want all to finish together. It helps the ones that aren't ready hurry up but the plants that are behind won't bulk up as much as the plants ahead but at least you can harvest at the same time.