Hey BigSlim how's it going? My first grow was MG too and I had terrible cal/mag problems, but I also was using the wrong stuff to ph down, had all kinds of crap going wrong.
Are you checking your ph? I think you'll be real happy with soil and oc+, all you have to do is water ph'd around 6.8.
I think your plants look great, is the big girl actually growing into the light?
Don't know if you're familiar with supercropping but it works great, it's a fancy name for breaking the stem and it looks like it would work great for you.
All I do is break the stem, a good 8 inches at least from the top. I don't mean bend it, I mean break it so the part after the break falls over. It's kind of like chopping a tree, aim the break so it ends up in a good spot away from other branches if you can. Within a day or so it will have turned back to the light and started growing again. It will buy you some space.
I've probably done it 20 times and never lost a branch, it works really well. The biggest problem is making sure you break it enough, if you don't in about 3 days it will look like you didn't do anything.
Here's a pic of the break when I supercropped the bagseed 5 days ago
I took this next pic yesterday. The horizontal stem is the main cola that I broke... and you can see it curves back upwards to form the bud in the pic.
It's a nice tool to have in the arsenal when you're trying to keep them short.