I am also in Oviedo. Couple things. I am assuming you are using Do It Yourself Pest Control on 419/Broadway. Rebecca and Matt are very helpful to home owners and will be a good resource to help you along the way. I will advise you that with their products - you will be paying way above market rate for the products to get that advice. As Ric suggested look at your PH. They provide this service for $1 per sample. I suggest doing a couple samples from different areas around your lawn to get a accurate reading of the entire property.
I suggest looking at slit seeding and not overseeding. Seed has become way to expensive to risk the lower germination rate of overseeding in my opinion.
I am going to try to send you my phone number in a private message. I am not sure if your post count will let you get a private message. If you do not have one from me post a couple more post here and I will be able to send you one eventually. Feel free to give me a buzz. Maybe I can help sort of a couple of options out for you.
10% of your customers are 90% of the problem.
You may think the grass is GREENER on the other side, but if you take the time to water your own grass it would be just as GREEN.