Large cracks after building work

[Iloverupertp]

I recently had 3 rooms downstairs converted into large kitchen diner.this involved two steel beams inserted and new bifold doors
I'm am gradually noticing more cracks on the middle and top floors(it's a 3 storey terrace )
The biggest crack is on the top landing (see photo) with cracks also on the middle landing,bathroom and 2 bedrooms
The builders have said it's fine and building control said it could be down to builders not propping up correctly when putting steel in
His advice was to take photos and keep an eye on not getting worse
The biggest crack hasn't got any worse but there are more smaller cracks appearing all the time
Should I be worried or is this quite normal ?
Tia

Normal for a month or two but it shouldn't last long before stabilising.
Talk to your SE who did the design as they should have checked the loads on the foundations. Adding a beam concentrates the loads at each end so causes settlement. Ours insisted on a new pad foundation I think 600x600x1000 to be able to spread the loads from a post into the clay soil. Even so we still got a little cracking in the bedroom above but less than a millimetre.