Good day everyone, a few months back I grew some marigold seeds in a pot and two of my plants have sucessfully come up with one full grown. However my marigolds seem to be experiencing trouble from start. The blooms dont seem to open at all and the stems at the blooms are elongated. The plant leaves also tend to frequently get sun burned thus drying up or wilting at the branches thus making them look dried. I have noticed that a white patch tends to appear across the top of the lush green leaves before this. As a result I have a large odd looking marigold that is browning from down up which hasnt given me a proper flower to date. The weather around here is that of a tropical climate so its usually sunny throughout the day from morning to evening, unless there are rainy periods between. Please advise and thank you for any information in advance.
The photos are not terribly clear, making it difficult/impossible to see the foliage clearly. One thing that can be seen though is the soil level in the pot, which appears to be halfway down the inside of the pot, though it's not possible to see how deep the pot is.
Your marigold seems to be a Tagetes variety and seems quite large - it certainly could be the case that it does not have enough room for its roots, unless the pot is very deep. There are also quite a few completely bare stems towards the base of the plant - this would suggest either insufficient root room, insufficient water or insufficient light, maybe all three. However, unless your mairgold is one of the Mexican varieties, these plants are only annuals, not perennials, see here https://homeguides.sfgate.com/marigolds-perennials-annuals-63218.html. You say you grew this from seed 'a few months back' - depending on how many months it might be coming to the end of its life.
If you think it might a Mexican variety, I would suggest you cut back the bare stems to about an inch or so and repot it in fresh soil, this time filling the pot up to about an inch below the rim, water in well, and see if it produces new growth.