HELP! I am losing my supply😭

My baby girl is 5 months old today and only gained 4 oz. in the last month. I noticed my supply has been dropping, but I didn't know how bad until she had her monthly weigh in. Can anyone give me advise on how to get my supply going strong again? Baby hasn't been acting different and has enough wet diapers, but her weight gain has been SO slow. Any supplements? Foods? Anything?