It depends...

If I understand you correctly then on the router of your current internet provide you have you Philips Hue, Toon and some other devices connected via a network cable. I assume that you have connected your DECO on one of the ports of that router.
I have a similar setup; some devices connected directly on the router and some via a switch connected on the DECO. And that works fine for me.

Then why "it depends"?

Well, the devices connected via the DECO will have an IP number like 192.168.1.xxx while the devices connected via that router have an IP number like 192.168.2.xxx. And that might or might not be a problem.
If this is a problem is your case then you could consider to place one of the DECO near your current router and connect to that DECO a switch. The Philips Hue, Toon and the other devices you then connect to that switch instead of the router. That way all the devices will be in the same IP number range 192.168.1.xxx.

Which switch? The TP-Link TL-SG108 you can buy for less than 30 EUR and has 8 x 1 GB ports in a metal case. For a few EUR less you have the 5 port version. But any switch will do.