Help with home assistant multi switch automation

I am somewhat new to home assistant and looking for recommendations with an automation. I have an automation to set multiple lights to 50% brightness and I notice two things:

  1. Sometimes there is a delay or timing issue where the lights turn on at different times. Is there a way to make it more reliable that they all turn on at the same time?

  2. I have noticed some lights get stuck with bad flickering when using my automation. Do I need to be adding in delay or a ramp up in the automation? Turning the lights on at the switch and changing brightness never causes the flickering. Light bulbs are Philips ultra definition LEDs.

Thanks for the help,