I've grown Nirvana White Widow. I got the seeds from Nirvana directly, not some middleman company. I had very good success with their strain and have grown it several times. The last time I grew it ( from clones of one of the original seeds ) I had the flowering time go for a full 12 weeks befor the trichs changed color, as opposed to the 8 or 9 weeks that they originally flowered from. As this was from clones I had a heck of a time figuring out just why they took so long to ripen as opposed to earlier grows.
Checked my humidity, temps, and nutes for changes. And checked for light leaks. The only thing I did differently was in the use of super soil and I don't know yet if that had anything too do with it.
After all that I did figure it out finally,,,, It was that my 400 watt hps lamps where over 1 and a half years old, Although they where still working, putting out light, I have since found out that older lamps do not put out the light or light spectrum that is needed to grow healthy plants to a good finish, even though they look like they are working properly. I got to talking to my hydro store manager and she was telling me how the 'big boys' always change their lamps out after their third grow, or once a year, just because of this problem. I changed the lights and voila, my remaining blue dreams started doing what they are supposed too be doing, even though they are about 3 weeks past due for ripening. The trichs are full and frosty, no amber yet, but definately better than befor and on the way to being a good harvest.
I hope this might be of some service to your problem