The buffs were to the mana costs for his Q and E abilities. His Q now costs 55 mana at all ranks instead of a steadily scaling amount, and his E now costs 50 mana instead of 60. The two adjustments make his usual combo cost a little less, giving him more room to deal damage in the top lane or in the bottom lane as a support.
Oddly enough, a dev corner post on Wednesday by Andrei “Meddler” van Roon specifically stated there would be no further buffs to Ornn in the Patch 7.19 cycle. The concern is that further buffs could be over-tuning him while it’s possible many of the problems with the champion stem from players using him for the first time.
But something clearly changed, even though the buffs are small ones. On the bright side, Ornn has escaped the 30s in terms of win rate percentage, as he sits at 45.88 percent in the top lane. The further changes might be enough to put him closer to a healthy 50 percent, as continued buffs have steadily increased his win rates.