Look up iron chlorosis. There could be a few different causes.

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Your plant presents several hallmarks that indicate the plant has been chronically over-watered (or under-watered). The interveinal chlorosis (yellowing between leaf veins) is usually indicative of an iron (Fe) deficiency, which can occur even when there is an adequate supply of iron in the soil, but it has become unavailable. Soils that drain poorly have low oxygen levels which cause Fe and Mn (manganese) to become electron acceptors. This leads to the precipitation of both (making them unavailable for uptake), even though these elements might be present in soils at normally adequate levels, and the plant’s inability to assimilate them. Soggy soils also make uptake of Ca(lcium) difficult or impossible, and the hooked and misshapen new leaves bear witness to a lack of Ca, which there might also be an adequate supply of in the soil, but it's unavailable. Finally, the necrotic (dead) areas of tissue at leaf tips and margins is almost certainly caused by the inability of roots to function normally, this, due to the lack of oxygen that accompanies waterlogged soils.

The fix is not to supply products that provide more of these nutrients. The problem would be best resolved by correcting the cultural conditions causing the stress, stress being the result of the plant operating near to or beyond the limits it was programmed (by Mother Nature) to tolerate. Things to do to correct the issues: 1) The next time your plant needs water, flush the soil thoroughly. Do this by slowly pouring a volume of room temp water, equal to at least 10X the volume of the pot the plant is in, through the soil. This will flush out any accumulation of salts due to tapwater and/or fertilizer salts. 2) A day or two, or three, after flushing the soil, fertilize with a production strength solution of an appropriate fertilizer. You won't likely come across a better fertilizer product than Foliage-Pro 9-3-6,

Which is a complete nutritional supplementation program from a single source. It is an excellent choice as the 'go to' fertilizer for almost everything you might find yourself growing in containers. 3) Get your watering under control by using a "tell" to help you determine what an appropriate watering interval is for each individual planting.

You might want to consider reading up on how to determine how appropriate a grow medium is, how to amend a poor soil, and how to make a far superior product to almost any commercially prepared medium you're likely to find, at a fraction of the price.

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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 plenty of air (oxygen) in the soil to drive root function. Many off-the-shelf soils hold too much water and not enough air to support the kind of root health most growers would like to see; and, a healthy root system is a prerequisite to a healthy plant.

Watering in small sips leads to avoid over-watering leads to a residual build-up of dissolved solids (salts) in the soil from tapwater and fertilizer solutions, 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.

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