Let's see if I understand this. Please correct me where I'm wrong. You already had an existing lawn, and the dog peed leaving brown spots. You did something to prep the spots and put seed in. Is that about it?

Where do you live?

A different approach to dog pee spots is to apply a handful of table sugar to each spot. That sugar stimulates the biological activity in the soil to process the urine faster. The grass usually returns to green all by itself in 3 weeks. What this means is your lawn is on the unhealthy side of normal. You can fix that by applying an organic fertilizer at least once a year. (and here's where you write back to tell me you have been fully organic for 5 years)