Leaves are dying but buds don't have any amber trichomes

Most people harvest when you observe ~5% to 20% amber trichomes. As a rule of thumb, this maximizes milky heads and minimizes clear heads. With that being said, strains differ greatly. I personally harvest slightly early because I can always turn trich heads amber, but I can never go back to milky (not without chemical assistance requiring the same ingredients as extracting ore from rock). Your top cola is how I'd want those lower colas to look before I cut. Once you have an idea of how a given strain looks when she is ready to cut, you can go off that. Maybe a week, 10 days tops?