We need more information.

Do you know what they used to treat in June? Because June is a month or two early to treat for grubs. Was it early or late June? If they treated too early, then that treatment didn't do anything, and then it could happen that you get grubs after the treatment. Based on what you've said I would not rule out a disease.

Can you post a picture of the area?

Where do you live?

What is your watering schedule (how often and for how long)?

What kind of grass do you have and how high/low do you mow?

I live in central Massachusetts,

I was applying 1/2" of water twice a week Sundays and Wednesdays for a total of 1".

The lawn is made up of KBG and tall fescue and is mowed to 31/2".

The first grub treatment was on 6/28/15.

Based on the watering frequency and amount I would be more inclined to treat for disease. We talk about watering infrequently. Infrequently means once per week if the temps are in the 90s, once every 2 weeks with temps in the 80s, once every 3 weeks with temps in the 70s, and once a month the rest of the year. If you had temps in the 100s then your watering would be more appropriate. The way you were doing it did not allow the surface of the soil to dry out completely. When the soil is wet all the time the microbial life changes somewhat toward a swampy biology and allows disease to get started. Normal turf grasses prefer dryer soil and can suffer when they don't get it.

When you take a picture, see if you can get up to 3 inches away and take the picture in the shade or on a cloudy day.

The newer Grub-ex1 (if that was used) formulation is very slow in moving through soil and can remain effective for quite a long time. So it could have to do with a dosing issue... or possibly it was too dry in around and after time of application not getting it down to grub depth in time? The older formulation....not as slow.

Also if you read up on some univ sites on grub control (michigan state comes to mind?) they have found that many "insect/grub" products are very ineffective against grubs...and also that timing is very important (bags often say very wrong dates).

Unfortunately many lawn care companies aren't the best or most knowledgeable when it comes to best practices in disease/problems (or fertilizer timing/types).

Their second application should have been something like Bayer 24hr Grub control - otherwise it won't have time to make it down to that soil depth for the kill.

Found: http://msue.anr.msu.edu/news/how_to_choose_and_when_to_apply_grub_control_products_for_your_lawn