Sunburn or fungus,please help total begginers

[Alexa_ion]

Hello everybody,

I am trying to help my father who has some problems with two of his flowers.Two of the plants have begun to show some worrying dark spots on the leaves and sume discoloration .I need some help with what the best treatment would be and maybe how to prevent this from happening again.We are total beginners on this subject,any help would be greatly apprecited. Also i am not sure the pots he uses are ok.
I will post below a photo with all his plants with numbers so we can identify them easily,to see their position and pots.And afterwards with the two specimens that have problems.Can you please help me restore them back to health and improve their well being









?

Thank you so much