Hello all!

So I need some advice. I have a little Serissa Foetida, and when I say little, I mean its adorably small. It's brand new, just got it for my birthday and I've had it for maybe 3 weeks, so not even a month. Unfortunately, on one branch and it's off shoots, the leaves are just completely drying out. There's an occasional yellow leaf or two throughout the bonsai, but this one branch is dried and another branch is showing the same signs. I remember hearing that bonsai die from bottom to top??

Also, when I first received the bonsai (beginning of June), I immediately repotted it with my mix of Al's Potting Mix. Once done with that, I also have been fertilizing it once a week with Dyna Gro's 9-3-6 formula at a half dilution (1/2 teaspoon per gallon). I water it daily. It also lives on a west facing window since I don't have a good south facing window for it to live. For the past week I've been submerging it daily in water out of fear of it drying out. This isn't my first race with a Serissa, but I kept my previous one alive for a few months before it died. I also have an azalea and hibiscus that are flourishing.

Have I just not found the right regimen for it yet? Did I shock it with repotting? Am I overwatering? Underwatering? What should I try to do to bring it back from this weird drying out?