What is the soil like this is growing in?
What is the soils pH?
What is the soil nutrient balance?

Have you looked closely for scale insects? They can be hard to spot sometimes.

Let's see a good close-up of those blackish fuzzy dots! I suspect that ginkgonut might be correct about scale insects.

Also, you ought to address some of those soil questions, too? In your location, I assume that this plant is outside in native soil, correct?

well its growing in a mix of compost,potting soil and perlite and the pH is about 5.8. im not sure of the soil nutrient balance. well ive looked but im not exactly sure what they look like. i'll goggle them. where am I most likely to find them? rhizo, no there growing inside in my 3 tier GH. i can't really take a close up of them cuz my camera just gets fuzzy when i try lol. but the weird thing is when i take them out of my GH and put them next to it, the leaves stop turning yellow and dying.

If the plant is growing in a pot check the roots for root rot. If the plant is outside has there been a great deal of rain? If the roots are black, soft and the outer surface pulls away then it's root rot. The leaves will curl and die. Also the plant's health is compromised leaving it vulnerable to other diseases. Root rot (Phytopthora) is a fungus. Root rot is a common problem with Miracle Fruit/Miracle Berry when the pot is waterlogged.

The miracle berry tree seems very fragile and often is vunlerable during the first year or so, but after the first year it tends to thrive. I found that if you think too much and give it too much attention then it suffers, its best to just plant lots of seeds in a variety of soils and then the strong ones will flourish, dont give it any unnatural feed, but give it plenty of rotting veg and manure, dont give it tap water, try to leave them outdoors, they are wild plants. Dont over water either. If you are in a dry area without rain then water them once a week. They grow wild in Africa and here it sometimes doesnt rain for weeks on end but they still survive, its their natural instinct to suck up water when available so if you give too much water its like over feeding a goldfish.

Here is a link that might be useful: Miracle berry