Hi Sapote,
Thanks for your insight. You are right. Unfortunately, the plant is declining even after a repot. The potting was done almost two weeks ago, but I began to notice it under stress about a week later. But you brought up an interesting point on the tomato seedlings. Do you mean tomato plants released some toxins into the soil that damaged the mango roots? In fact, I had mixed a bit of nursery soil that was remaining in another pot to make up for the volume.. I wasn't aware it was laden with tomato seeds. Lesson learned!
Currently, the temperature in Kathmandu ranges from 65F to 85F.. with rain showers. The pot was safe from rain.