hairs in general arent a great thing to go by, they come in waves so some are older than others, auto ones do go brown i think youve combined the tric and hairs in your head, sometimes the trics dont amber up.
looks like it could go longer personally but if youre after a more up high then maybe you want to take it earlier than i would. i try to wait till around day 80+ but obviously the strain will change that.
they put on most weight near the end id say yours will get a bit fatter if you leave it.