In an extremely high % of cases, necrotic leaf tips and margins are caused by over-watering, an excessively high level of dissolved solids (salts) in the soil solution, or some combination of the two. High root temperatures, nutritional imbalances, ammonium toxicity, and phytotoxicities (things poisonous to plants) like air pollution can also cause or contribute to the physiological disorder causing the symptoms. In most cases, the greatest amount of traction is to be gained from making sure your watering appropriately and flushing the soil of accumulating salts when you water. If you can't water appropriately w/o limiting normal root function or root health, you might want to take a look at the soil you're using. In any case, getting to the point where you can water to beyond the point of total soil saturation, so you're flushing the soil when you water, without having to worry the soil will remain saturated for an extended period, represents something of a breakthrough for the grower. When you find yourself at that point, it is much, much easier to consistently maintain your plants in a state of high vitality, which means you don't have the unsightly symptoms to remind you that the plant is being asked to tolerate something it's not genetically programmed to deal with. I'd start using a 'tell' to 'tell' you when it's time to water (see more below). I'd also keep learning more about how much impact soil choice has on your potential for consistent success. A General Overview (click me) Using a 'tell' Over-watering saps vitality and is one of the most common plant assassins, so learning to avoid it is worth the small effort. Plants make and store their own energy source – photosynthate - (sugar/glucose). Functioning roots need energy to drive their metabolic processes, and in order to get it, they use oxygen to burn (oxidize) their food. From this, we can see that terrestrial plants need air (oxygen) in the soil to drive root function. Many off-the-shelf soils hold too much water and not enough air to support good root health, which is a prerequisite to a healthy plant. Watering in small sips leads to a build-up of dissolved solids (salts) in the soil, which limits a plant's ability to absorb water – so watering in sips simply moves us to the other horn of a dilemma. It creates another problem that requires resolution. Better, would be to simply adopt a soil that drains well enough to allow watering to beyond the saturation point, so we're flushing the soil of accumulating dissolved solids whenever we water; this, w/o the plant being forced to pay a tax in the form of reduced vitality, due to prolong periods of soil saturation. Sometimes, though, that's not a course we can immediately steer, which makes controlling how often we water a very important factor. In many cases, we can judge whether or not a planting needs watering by hefting the pot. This is especially true if the pot is made from light material, like plastic, but doesn't work (as) well when the pot is made from heavier material, like clay, or when the size/weight of the pot precludes grabbing it with one hand to judge its weight and gauge the need for water. Fingers stuck an inch or two into the soil work ok for shallow pots, but not for deep pots. Deep pots might have 3 or more inches of soil that feels totally dry, while the lower several inches of the soil is 100% saturated. Obviously, the lack of oxygen in the root zone situation can wreak havoc with root health and cause the loss of a very notable measure of your plant's potential. Inexpensive watering meters don't even measure moisture levels, they measure electrical conductivity. Clean the tip and insert it into a cup of distilled water and witness the fact it reads 'DRY'. One of the most reliable methods of checking a planting's need for water is using a 'tell'. You can use a bamboo skewer in a pinch, but a wooden dowel rod of about 5/16” (75-85mm) would work better. They usually come 48” (120cm) long and can usually be cut in half and serve as a pair. Sharpen all 4 ends in a pencil sharpener and slightly blunt the tip so it's about the diameter of the head on a straight pin. Push the wooden tell deep into the soil. Don't worry, it won't harm the root system. If the plant is quite root-bound, you might need to try several places until you find one where you can push it all the way to the pot's bottom. Leave it a few seconds, then withdraw it and inspect the tip for moisture. For most plantings, withhold water until the tell comes out dry or nearly so. If you see signs of wilting, adjust the interval between waterings so drought stress isn't a recurring issue. Al

Definitely looks like you have a scale infestation to me. theyre a small hard bodied insects. thay attack the leaf by sucking sap and nutrients from the plant and if not corrected the plant will die. scrap them all off with your fingernail. Check all the leaves top and bottom, stems, and every part of the plant. keep them segregated from any other plants. If they've been around others, inspect those two as the scale can easily spread. also, not related, but hopefully those plastic cups have holes in the bottom.

I wrote this as a reply to something over on the botany forum and figured I'd be able to use it from time to time, so saved it. Let me know if you want anything explained a different way: A higher degree of expression of the pigment anthocyanin (which expresses the color red or purple) in juvenile foliage is very common throughout the plant kingdom for a couple of reasons. First, even though the pigment absorbs light w/o being a part of the photosynthetic process, it plays a photoprotective role for new leaves that emerge under high light conditions ...... when they are in an ontogenetic stage that make them more sensitive/vulnerable to light over-saturation. If you were able to quantify it at home ..... the reduction in anthocyanin's expression would be seen to correspond with a decreased need for photoprotection, this, because photosynthetic maturation allows leaves to utilize higher light intensities. A major consideration (that occurs during photosynthetic maturation) is an increase in chlorophyll, the pigment often referred to as 'nature's sunscreen for plants'. In short, the red coloration disappears as photopigment concentrations and leaf cuticle thickness increases, both of which would be occurring as mesophyll underlying the leaf cuticle differentiates into separate layers (pallisade and spongy). Second (but probably not a consideration in F benjamina), the red coloration is also very often associated with an increase in phenolic compounds that serve as defense against insect predation or herbivory by making leaves unpalatable. It's also thought in many circles that the red coloration may make leaves more difficult for some insects and herbivores to see, and may signal insects that the affected leaves are a less nutritional food source than bright green foliage elsewhere, or that it would make a poor receptacle for ovaposition (egg-laying). Al

Can you post a pic pls? Can you tell us what kind of soil you've put it in? It's hard to make any suggestion w/ no pic & so little info. We have no idea how you've been caring for it.