Sad starter? Time to start over?

I’m having great difficulty with my starter at the moment and I need advice from the pros. Ive had this starter for 3 weeks, it bubbles a lot and looks happy but refuses to rise more than half its original. I’ve had so much success with this same starter recipe in the past but this one just refuses to do anything This is 12 hours after feeding. Ratio is 1:4:4 (Half wheat and half unbleached bakers flour)

I’m having great difficulty with my starter at the moment and I need advice from the pros. Ive had this starter for 3 weeks, it bubbles a lot and looks happy but refuses to rise more than half its original. I’ve had so much success with this same starter recipe in the past but this one just refuses to do anything This is 12 hours after feeding. Ratio is 1:4:4 (Half wheat and half unbleached bakers flour)