Baby poop 9months

My girl will cry when she trying to poo. She will strain herself too. We went to the doctor and she is taking stool softener that was given. She is on solid and drinking friso. Her poop however is not hard pebble like. It come out average/big/long size and is not dry. Will it be wise to change her milk? We changed her milk to stage 2 at the same time we started her on solid. So we are not sure if friso stage 2 is the cause.