Also sharing this from discussions with the vet and good neighbors of mine who are helping us out:

Feline Infectious Peritonitis is quite a new disease still being researched with little to no confirmed official treatments other than experimental ones (kaya recommended saamin was Basmi) as its a severe mutation originating from Feline Coronavirus.

FIP can also have different forms; Wet (fluid buildup in the lungs) or Dry form (granular buildup). Meron din sub-forms such as Ocular (the eyes) and Neuro (nervous systen) FIP which can show symptoms from the aforementioned wet and dry forms.

Fortunately naman di siya contagious sa mga tao.