Help Non linear Growth Models - Derivates

Hi!!! im amateur in mathemathicals growth models but im doing my graduated work in adjust five differents models in some growth parameters in onion,

So my doubt is basically in a derivate for gauss model, i cant derivate this model and it had been adjust for some parameters. So i need to know a derivate for continue my growth analysis.

Also, I just dont know if a sentence of that model is right or wrong, same for others models and their derivates. I read some books about nonlinear models and found diferents expressions in Monomolecular, logistic and Richards models, so i put as options (1 and 2). I also have doubt which are right. Finally i didnt understand which values could have parameter M in richards model.

Ill be so grateful with your helps. i'm not physic student, i'm agronomist so you could know better,