This is called a “popcorn effect” and is a known issue with SmartThings right now. Unfortunately I don’t think Trendsetter will work because of the way the SmartThings/Hue integration works. (It would work for most other kinds of lights, but not all. )
The smartapps that have support for Hue scenes created in the Hue app itself should work much better, so look for that distinction as you review the choices.
You can see discussion of this issue, which unfortunately has been going on for about a year, in the following thread (this is a clickable link)
There is a new official device type handler which was released a couple of weeks ago and is supposed to help with this problem, so you might want to switch to the new device type handler if your devices are not using it.
Otherwise, the only really solid way to fix this is to create a Hue scene in the hue app (not the SmartThings app). And then activate the scenes through the free IFTTT service or through one of the smartapps that can trigger those scenes such as the one @Sticks18 mentioned . That way the group command will get sent by the hue bridge as part of the scene and you should have much less of a popcorn effect as well as eliminating the problem of some bulbs never getting the message.
Using IFTTT is a little easier than using the smartapps because you don’t have to re-add the hue bridge to your SmartThings account, so you might test with that method first to see if it does make a difference.
That might add a little lag upfront because of IFTTT, but once the message gets to the hue bridge operation should be much smoother.