My baby is struggling

Cris
I am a mother of 7...yes 7 kids. My daughter Itzcali was born on 01/19/17 and I have never had my other kids struggle with weight gain. I nursed all my kids some longer than others. My daughter has hypotonia. Its basically poor muscle tone. Has anyone else has their baby go thru this? Its also known as floppy baby syndrome. I have gone thru an emotional roller coaster these past few weeks. I literally thought I was starving my baby because I would feed her for what seemed like all day and she would not gain weight. Now my milk supply is down and I have no idea what else to try to boost it up.. Ive done fenugreek pills...mothers milk tea...oatmeal and flax seed...water is all I drink...and I nurse her all the time. She does get fortified breast milk and formula per Dr orders but I don't want to stop nursing 😕 anyone out there willing to make other suggestions?