Trouble Shooting HID lights and horn install (what did I fuck up?)

Hey Tacomaworld car gurus, mechanics, and DIYers, I could definitely use some help if anyone could advise me on trouble shooting.

Background, I installed morimoto HID lights into my low beam headlight about a year ago. Other than failing to retrofit my housing like an asshole (seperate issue I need to fix), they just stop working this afternoon.

About 2 days ago I installed my 4 horn American auto horns from the Tacomaworld group buy. Those were also working until this afternoon.

So it looks like simultaneously both my headlights and my horn are no longer working and I'm not sure what caused the issue. I've already tried to disconnect both the HIDs and horn to see if I could get either one to work individually. I removed them from the ground that is by the battery and tried each individually but neither are working. I also removed them each from the positive part of the battery and tried them individually but that did not work either.

They worked for about a day together but now I'm at a loss on what to do. Could it be a bad ground since I'm sharing the ground for high the horns and the HIDs? Did I fuck up a fuse?

I do not have a volt meter to check but will get one tomorrow. I also don't know what to check once I do get a voltmeter. Would I just check the voltage of the positive and see if it was 10 volts and check the ground to make sure it's 0 volts?

Other than buying some halogen bulbs to go back to stock and trying my stock horn again, what else should I trouble shoot?

I'm far from a pro at any of this. I've stumbled my way along with wiring a remote start, new speakers, and wiring my 3rd light on my shell so I'm not a total newbie. But im at a loss right now and my truck is not street legal anymore without low beam headlights.

Edit: my high beams and day time running lights work. And my interior lights work too if that helps narrow down the issue.