Network setup and upgrades

Hi there guys

First of, let me start by saying thanks to all of you for such great work in keeping this awesome forum going!

I really hope I'm posting this under the right category.

My network setup at home is what I believe to be somewhat, extensive and it has worked for the last two years without a major glitch!

Let me state what setup I have and how I'm running it to be on the same page.

We live in a two story house where I have a dedicated media closet in the second floor.

The setup in the closet includes:

1T. Time capsule

24 port Ethernet switch

Mac mini (media server running)

Whole house music system with seven (7) airport expresses A1264, that stream music to separate music zones throughout the house, The AE are working wirelessly in the back of multi zone amplifiers and are named by their zones like, Office, Master Bath, Girl's room, Boy's Room, Kitchen, Garage and Outdoors.

Of course, that's how it appears on all of our iphones under Airplay.

We also run 4 apple tvs, one per room. Those are wired.

In the first floor we run an AirPort Extreme running on Bridge Mode connected to the switch in the media closet second fl.

To extend our wireless signal further, there is also an airport express in the boys room and another one in the back yard.

On the electrical side of things, we are running several Wemo light switches in different areas of the house that have also proven to be very solid as far as wifi connection and two Nest Thermostats.

Everything gets operated by five 5S iPhones and four iPads.

You can say that there's always something happening wirelessly in our house.

Here comes the issue (at last! Sorry guys...)

Trying to reinvent the wheel this past weekend, I bought two brand new AirPort Extreme units to replace my old ones. Thinking into the future and with the new ac wireless signal etc. I get to the house, set them up the same way I had the other ones and everything has gone upside down. I run the airport utility on my Mac mini and although I can see all my AE's, not all of them connect to the system. I've tried everything from resetting them to resetting the AirPort Extremes. It's like the extremes would reject them.

I read about the ipv6 issues with the new extremes and even turned that off but it did not solve the problem either. Even some Wemo light switches went missing also.

Funny thing is I reinstalled my old units back and everything went back to work like it always did. Wonderful!

My question is, am I doing something wrong?

Am I missing anything?

Should I just forget the whole thing and return the new units and forget about progress???...........:(

Any help you send my way, will be more than appreciated guys .

Thank you so much in advance.