Due to regional variations, let me tell you what I would do if you were in the southwest with the same problems and at the same weather conditions for me.
First thing, its about time for me to strip the lawn meaning dropping the mower blades all the way down and almost scalping the lawn. Then I would rake up the leavings and do some de thatching that has occurred.
Then this leaving would go into my gardens or beds and worked in for mulch.
Then I would consider airation. I do this every four to five years. I rent an areator and be sure to have one that actually takes plugs of sod out and does not mash down the earth to make those dimples. Your goal is to add air and to de compact the soil. Rake the plugs off the lawn and take to the composte pile or to a bed and work in again.
Now, if weeds have not emerged, then add a pre emergence weed and feed fertilizer with a ratio of 3-1-1. Meaning high in Nitrogen and low in the other two ingredients. In the fall reverse this ratio.
Now use a good broadcast spreader and do a checkerboard pattern disbursement. The fertilizer should fall down in the holes nicely.
Now, water in the fertilizer slightly, you want to break down the pre emergence so that it can begin to work immediately, the fertilizer especially if Scott's has time released stuff.
Now, grubs are everywhere and in even very healthly lawns. The migrate to the lawn with the most lush grass for the eating of the roots.
In my opinion, grubs are like fire ants, you do not actually kill them you move them to your neighbors and beyond.
Now, get a good fan type hose end sprayer and buy some liquid concentrate Dursban or Diazon and spray the lawn pretty heavily. With the areatin the chemicals will get down to the roots faster and work faster too.
Remember, when it rains, the insecticide will wash away and its gone, so re apply after any rain what so ever.
This ought to get you on the right track.
Set your blade where it only takes off 1/3 the height every mow. any more it sends the grass into a slight stress.