First, check the temperature of the tank and possible raise it up to 80-82F. I would suggest to add a bit of rock salt but since you said you have shrimp in the tank, not sure which type so salt might be out of question. Sound like he is approaching old age. Think about this, at least he has his children continues living his legacy. Good luck.
Welcome to R2R.
The fact that you have his babies is a testament to your care and the fact that he will live on.
Their lifespan is 3-5 yrs but you never know how old they were when you got him.
Good luck and welcome to R2R