You don't say how long you've had the plant in the pot, but these are large shrubs - being constrained within a pot is likely the problem, because it restricts root space, and a plant can only grow as well as its roots allow. Yours appears to be a variety of HIbiscus rosa-sinensis, and the average height and spread for these (in the ground) is between 8-15 feet tall by 5-8 feet wide, but in order to achieve this and remain healthy, the plant needs to grow and spread its roots. Smaller flowers are also a signal of reduced root space. I can't otherwise see any infection/infestation problems from the images you've provided, though if its been in the pot a while, a shortage of nutrients might also be an issue, a problem that is also resolved by planting in the ground, when the plant is able to seek out for itself what it needs. Some clarification of what 'DAP' is might be helpful, along with what type of compost you added, as well as knowing how long it's been in the pot and what fertilizers you've used in the meantime, but it doesn't look particularly unhealthy, it just has the look of a plant that's restricted at the root.

You don't say how long you've had the plant in the pot, but these are large shrubs - being constrained within a pot is likely the problem, because it restricts root space, and a plant can only grow as well as its roots allow. Yours appears to be a variety of HIbiscus rosa-sinensis, and the average height and spread for these (in the ground) is between 8-15 feet tall by 5-8 feet wide, but in order to achieve this and remain healthy, the plant needs to grow and spread its roots. Smaller flowers can also be a signal of reduced root space. I can't otherwise see any infection/infestation problems from the images you've provided, though if its been in the pot a while, a shortage of nutrients might also be an issue, a problem that is also resolved by planting in the ground, when the plant is able to seek out for itself what it needs. Some clarification of what 'DAP' is might be helpful, along with what type of compost you added, as well as knowing how long it's been in the pot and what fertilizers you've used in the meantime, but it doesn't look like its dying, it just has the look of a plant that may be restricted at the root or is suffering environmental/care problems. Temperatures wherever you are might be having an impact too, so knowing where you are would also be useful; I'm also curious about the white 'flakes' present at soil level in the first image...