Is it normal for stomach bug came back

[Literallynoideaatall]

Dc have been ill with vomiting and diarrhoea, dc1 was sick twice one day, bad diarreah for a couple of days then seemed fine, until a week later when he started being sick again.
dc 2 exactly the same, was fine for 5 days and this morning has been sick again.
most of the week they'd been eating plain food (plain pasta, rich tea biscuits, dry toast and banana) but yesterday I gave him some slightly more normal food of beans on toast for lunch and a ham sandwich and some crisps for dinner and it's seemed to have made him ill again?
same for dc1 before he was sick again he ate normal food at his dads.
do I have to keep just giving them plain food? For how long?
cleaning up sick is my worst nightmare as a parent so I just want it to hurry up and end

Kids can become really sensitive to dairy after a stomach bug. Dd does so I have to cut it out for a few weeks (pain in the bum!) and slowly reintroduce it.

Probiotics can help - I get the optibac sachets and mix them with juice or soya yogurt for Dd which seems to work.

Yes, agree with the above poster. DC can take a week or two to be able to tolerate a full range of foods again after a stomach buy. Probiotics can really help and I used to buy lactose-free milk for a couple of weeks too, as ordinary milk would make them sick again.

I agree with the above Google temporary lactose intolerance

Thanks temporary lactose intolerance makes sense I'm going to try them with lactose free stuff for a while and see how it goes!
Poor ds1 just wants a McDonald's and thinks I'm very mean making him eat toast and soup!