So in the four-ish months since I've had my largest miracle fruit plant, I at first saw stability, then loss of foliage, and for the most part after that, nothing. No new growth, no loss of leaves, and I began to worry that: A, my plant was dead, B: it was defective, or C: I was doing something wrong. Because it was unlikely I would have a "defective" plant, and it would have been obvious if it was dead, I was probably doing something wrong. The obstacle of correcting this is that I didn't know what I was doing wrong. I contacted the seller and in short, was told to keep doing what I was doing. This was about a week ago.
Yesterday, I looked at my plant and noticed that a couple of leaves had turned brown, so I opened the bag and checked to see if there were more dying leaves. I didn't find any, instead to my delight I saw that at the top of the plant there were two perfectly formed flowers! I looked carefully, and found there were actually a dozen or so tiny buds growing on the branches, and a few small red leaves, which I think are newly formed. I took a cotton swab and brushed against both of the flowers to hopefully polinate them.
I think my plant has finally overcome its transplant shock. I just wish I could find what I was doing differently, so I can keep it that way.