Cold, loose stools. A new infection?

Hello, My daughter is 5 years old. She had a cold for the heat 2 week is. She was on augmentin and we have stopped that after a dosage for 5 days. She still had a nasal block but no cough or fever. It feels kind she has phlegm stuck between nose and throat mostly. If we get her to blow her nose, the mucus is mostly white. One or twice light yellow. Last two days she has been saying stomach pain on abd off, today she also had watery stools. She complained of pain in the lower abdomen on the left for sometime and then said she was fine. She went loose stools after that. So far she had gone only once. She's on montair lc in the night for the last month abd has a probiotic,  protectis,  in the night. Is this a new infection? Or could it be a sidde effect of the antibiotics although the dosage got done on Fri morning. Yesterday her poop was normal. Please advise. I'm worried.