Not just developers - anyone living far enough from the equator is suffering from this. This is in fact why lighter skin evolved, out of a need to get more vitamin D from the limited sunshine.
Take your Vitamin D supplements, a few thousand IU a day, probably more if you're not White. Get sunshine. Sit by a window.
It's particularly critical for men's health as Vitamin D is critical in the proper production of testosterone, as well.
Don’t sit by windows. Windows filter out the rays needed for your body to produce vitamin d. You’re essentially damaging your skin without the benefits
If you're mildly vitamin D deficient, you would probably want to take an additional 1000 IU per day in addition to the 1000 IU in your multivitamin. It's safe for most people to take up to 4000 IU per day, but unless you've been tested and know you're severely deficient then I wouldn't take more than 2000 IU total per day. Then just keep checking your blood pressure over the next 6 weeks and see what happens.
I'm not a doctor. I take ~2000 a day, sometimes 3000 when a third pill falls into my mouth from the bottle. Actual dosage advice would be better from someone who isn't just relaying anecdotes.
That said, I would guarantee that you're better off with that 1000 IU than with nothing!
Could also be Vitamin D deficiency, which is probably common among developers.