is it still THAT bad to add an ad to an adset on FB?

I have an adset of 2 ads. One performed way better than the other, so I turned off the second ad.
It it pretty profitable right now and I want to scale – the adset is super optimized, I think.
However, FB is warning me to add another creative into the adset, to limit ad fatigue.
If I add another ad to the adset, would it completely ruin the optimization already done with this adset?