I’d like to know if there is something I can do to close the gap or hide the gap in the blinds. Obviously, I can measure properly and purchase new ones but really trying to avoid that.
I’ve also thought about curtains, but it’s also something I’d like to avoid. Are there any solutions to this?
Here is another photo zoomed out. 
You could put a taller, bushier plant right in the middle. Or get one of those old privacy screens folded up a bit.
Buy one more set of blinds 3" wide and hang it in between these two. Just ask for “mini blinds” at your local big box store and they’ll put you on the right track.
Go to CVS. Buy one item. Hang receipt to cover gap.
You could try applying something to the actual window, like a fake wooden “pane split” whatever the real name for that is. Put one on the inside and the outside, so it doesn’t look weird. Just make sure the wood is weather proofed. Even the inside one will likely see decent humidity and moisture some seasons.
https://www.thistothat.com/cgi-bin/glue.cgi?lang=en&this=Wood&that=Glass
Options for the right adhesive.
Most places I’ve ordered blinds for will allow you to reorder a different measurement, up to a lifetime cap (like 4 times per person/household - you only get to fuck up for free so many times). The one I messed up they just let me keep because it was a custom size (still in my garage for some reason)
It’s a pain but it is the way to go if you want your blinds to really be good for the space.
Only time I’ve been annoyed was a cloth roller blind I ordered to cover a large door window that I measured perfectly but nowhere in the description did it say that there was a 1/8 gap at each edge and the overall width of the blind was 1/4" shy of your measurement. Returned that one and just got a bigger one where the blind was the actual width I wanted…
attached a vertical piece in front of the gap?
Glue a strip of material to the backside of each fin to extend coverage.
It won’t looks great.
I had the same problem - the correct size blinds I bought were broken and had to return them and could only get a set that was 1 inch shorter 😠
Ended up moving the mounts slightly inward so the gaps were on the edges. It’s a lot less noticeable than the gap in the middle. Ended up putting curtains up to cover the edge gaps, though it wasn’t strictly necessary. I keep them pulled to the side, and they’re purely decorative / to hide the edge gaps.
Moving it inward may be the way to go…
Definnetly get those mounts butt up against each other. Depending on what hardware is up in the blind track ( and it looks like the where set right with the adjusters to the outside ) you may be able to take a hack saw and trim the track just slightly like even a 1/16th off each end will end up getting that gap down an 1/8. Etc etc. Or you may be able to find a center style mount for a long single blind set up. And get the two ends in there instead of two end caps. It seems excessive BC there will always be some small gap.
Get braces.
Haha, I chuckled
curtains are the solution even if you are trying to avoid it. curtains help soften the corners of the windows, too.
Or two more large plants and center them around the gap.
I have a “center curtain” for this very reason. Depends on how much it hurts your soul to basically turn one window into two smaller windows.
A more complete picture would help, but my approach would be to move the blinds closer together, then fill any exposure that then occurs on the perimeter with something the same shade as either the wall or the blinds.
I’ve thought about moving them closer. I can do it without issue - I suppose I can try it out and see how it looks.
