There is a theory that strong light degrades THC contents in trichomes in the last phase of lifecycle. I’ve heard from several pro growers that it’s good to decrease light intensity in the last two weeks. One amber trichome that you spotted means there are hundreds of them already. Seems you’re close to harvest if the buds don’t increase in size anymore. Depending on the strain transition from milky to amber can take from 1 to 3 weeks. Simply inspect them every other day. When you clearly see at least 10% amber on buds (not leaves) it’s time to harvest.