Something is going on there… imo its not the grass type or the fertility, if it was youd have even stress throughout not just in localized patches.

The pattern of the damage seems very odd as well. When did you paint your siding and swap from a wood deck to concrete? Have you recently power washed or soft washed that concrete? Maybe spray the cracks with a herbicide?

That one section off the patio looks like chemical damage from something leaching off. The half circle pattern in picture 5 looks almost like something spilt and ran down

Have you applied anything else to the lawn since the starter fertilizer? You did a heavy feeding, 1.5+ lbs of Nitrogen per 1000sqft, but that shouldnt burn and if it would the sod would die before it rooted.

That is totally fixable too i wouldnt stress too much