Twin A smaller than Twin B

I’m 25w1d with fraternal M/F twins.. I had an ultrasound today and learned that Twin A is lagging behind growth wise by 19%.. the OB shared that 20% is when they start getting concerned.. she booked my next scan for 3 weeks out which seems long considering how close they are to the 20% threshold? Anyone else experience one twin w/ growth restriction? Any tips on how to help Baby A bulk up? (I know it’s mostly out of my control but can’t stand feeling helpless)