Baby lost weight after starting solids

Hi mummies! My baby is turning 7 months. We started giving him solids when he was 6 months old. After the first 2 weeks, he gained 400g. Then he had viral rash and lost abit of weight. After 1 week, he is still losing weight though he is now ok. He is very active and achieving his milestones. We feed him solids 3x a day, 30 mins after milk feed. Are we doing anything wrong? Or this is normal? #pleasehelp #1stimemom #advicepls