Getting back to the OP's problem, it's very difficult to diagnose lawn
problems without having soil samples tested, being able to physically
examine the problem area, knowing when and under what conditions they
occur, etc.

However, over watering and over fertilizing, especially in hot
weather, will lead to disease and fungus problems. If you're putting
fertilizer down in addition to having it professionally done, the lawn
is getting way too much fertilizer. In NJ, I fertilize mine once in
spring together with pre-emergent crabgrass control, then once in
early Sept, then again in late Oct. These are cool season grasses and
you want to encourage the most growth in the cooler temps. I believe
it's better to skip giving the lawn extra nitrogen during the hot
summer months as it can easily promote disease and fungus.

Regarding watering, it should be done deeply, 3/4 inch to an inch and
only as often as necessary. Depending on temps and soil conditions,
this could be from about every fourth day to once a week, assuming of
course it hasn't rained. A lawn is far better of being allowed to go
dormant from lack of water in hot weather than giving it a shallow
watering every day. The watering should be timed so that it's
finished in the early morning, like about 8AM. This avoids
evaporation during the hottest times and allows it to dry out without
being wet for a long period of time. You can tell if your lawn needs
water by walking on it. When the grass does not snap back and you can
see your tracks, it needs water.

I also agree with the advice to switch to the neighbors lawn service
company. BTW, what does your service have to say about the problem?
One key benefit to a lawn service is their experience over the years
and also seeing other lawns that exhibit the same problem at the same
time as yours. You should also see if there is a county agricultural
service available. Here in NJ we have that and you can take a grass
sample to them for advice.