Mucus in poo - 3 week old

Hi guys,

Wondering if anyone can share their experiences.

Our wee man is 3 weeks old. He was combo fed but my wife is currently on antibiotics and has stopped giving him breastmilk, so he is currently 100% formula fed.

Before, his poos were mustard yellow, textbook seedy texture but have been more yellowy-brown, thicker clumps with a lot of mucus. All his poos are quite stringy now...

But he is absolutely fine in all other aspects. Still feeds well, barely cries, sleeps well, seems happy in himself, alert and engaged when awake etc. He has no 'symptoms' of an issue apart from mucusy poos.

Going to mention to the HV but wondering if there is something I should be exploring further?