Why one of the plants looks like is being flushed when I still have more than one week until the end of the grow, and I didn't start the flush?

All plants are individuals and not robots that can read a calendar! Seriously though, even though the seeds came from the same packet, the breeders grow hundreds of plants to make enough seeds to supply the market. So, even though they came from the same packet, if you got 7 seeds, all 7 seeds could have theoretically come from 7 different mother plants. Even human twins/triplets do not develop exactly the same, so it is with plants. Even though the seeds have come from the same strain, each time seeds are made, there is random genetic re-combination taking place and this is what causes different phenotypes of supposedly identical plant strains. This is also what breeders and growers look out for, the next "super" plant that has adapted in some way to be a more outstanding example of a particular strain. Such things as; faster growing, better aroma, faster flowering, more trichome production, better ability to cope with stress, purple leaves, etc. and sometimes all of these things. If you took cuttings from these plants, I would definitely recommend the cuttings from the earlier finishing plant, as this means your total cycle will be a week to ten days shorter, an important consideration if you are paying for electricity supply! By the way, I applaud your choice of strain, having grown Jack 47 from Sweet Seeds (plug!) multiple times, I know you won't be disappointed with your harvest. Give it at least 4-6 weeks to cure properly and you will be amazed! Hope this helps.... Organoman.