The soil looks too dense. I treat my Pelargoniums somewhat like my succulents. So I make sure the media is well draining and gritty. But they get a bit more water than my typical succulents, especially when we get into the long zero rainfall months.
Looking at the leaves of your plant, it seems it is the older leaves dying away. So that is also a natural cycle that it does. I also see lots of new leaves, so overall your plant is still doing okay. I would just try to improve that media. Mix in some pumice or perlite to make it lighter.
I agree, do not apply fertilizers. It is in some stress, and basically I find, they do not really need a lot. I hardly fertilize my Pelargoniums here.
I grow my Pelargoniums in part sun/shade. Sun in the morning, and thebdappled light in the afternoon. They will burn here if it gets way too much sun and suffer our dry heat. Your area may be better humdity wise so you have much better growing conditions.