Does the LED fixture have the ability to dim? If so, I'd just set it to the height you want it at and then gradually increase the brightness over 2-3 weeks. The other option is to place some window screens (a few layers) under the lights and then remove one each week. This is what I ended up doing when I replaced my very, very, old T5 bulbs with brand new and better quality T5 bulbs. A third option that I have seen people do is to reduce the light period of the new lights and slowly increase the duration over a week or two.
