What the heck happened to my light strings...?

You know, my red/white/blue fairy lights in my office. That I love so much. :0)

These ones:

Are now down to this small section:

Everything else is completely dark.

Now I can't think that every single bulb blew. And this didn't start happening until I added that third stand--which was not the same brand as the first two.

So I'm thinking two things. My little fuses in each strand blew and I shouldn't mix and match strands because the voltage or wattage could be different.

And I have two choices. Either buy enough of the same lights to fit the space I want covered. Or remove the third strand and then go through the painstaking process of testing the bulbs in the remaining strands--after changing the fuses if possible.

Argh. Tough choice. Time is money, but those suckers aren't that cheap.