Hello everyone Can you tell me what mixture I can switch to so there i…

Hello everyone Can you tell me what mixture I can switch to so there is no hard stool in the child? Not that it's constipation, but it wasn't like this before, a solid lump comes out The mixture has always been Nestage, for a couple of months now the milk has changed The doctor said some kind of mixture, but it costs 12 thousand 300gr, I can't buy it. We've been giving him kefir and yogurt, and soups he eats Is it normal stool sometimes? I sometimes give him Dufolka I'm afraid there might be hard masses inside.