Hi, My 3 Years Old Daughter Was A Bit Constipated

Hi, my 3 years old daughter was a bit constipated 2 days ago, yesterday, without change her diet much, just giving her more fruit as usual when she starts to be a bit constipated, she had a running poo with a very bad smell but today she had another big running poo with a very strong ammonia's like smell. This never happened before and I'm a bit scare as she born with epispadias and horseshoe kidneys, I'm always thinking if she is getting a bad infection somewhere. I've been reading what I can find about this matter but there is no much information about it or at least someone whom match with my daughter case? Should I just change her diet for more fibre and give her more liquids or that just goes with time? Or can it be a symptom of something that I should be really worried about and take her straight away to my GP?