How to disable UART service?

Each custom UUID is 128 bits (16 bytes, plus the 2 byte header) so you can't fit all 3 into the ~20 byte scan response (which is the default).

However, you could put them into different advertising packets and alternate between them (you're already alternating between your custom one, and the default which is specified with {}.

So:

const adv = ...;
const adv1 = [ 17/*length*/, 6/*128 bit UUID*/, ...16 bytes of UUID... ];
...
NRF.setAdvertising([adv, adv1, adv2, adv3, {}],{ .... })