Kindly identify this plant?
Is this Plum plant?(identify this plant)
I have no idea what it is but it needs some help to survive. Looks to me to be a nutrient deficiency. I would think it is an iron deficiency by the green veins yet yellowing leaves. It could be due to other deficiencies or the plant's PH level off which hurts the plants ability to take up what it needs to be healthy.
I would check if the soil PH is either high or very low.
I would do a foliar feed high in iron. I would add a neutral full spectrum soil fertilizer which not only has the usual (nitrogen(N) - phosphorus(P) - potassium(K)) but also all the micro nutrients. Start small and add slowly. Too much is harmful too.
Never add fertilizer to a very dry plant. It could drink up too much too fast and get fertilizer burn.
I am not familiar with the color change pattern in your last photo, but again a broad spectrum with micro nutrients should help.
Some articles I think might help.