My little one had a stomach bug for several days and and lost weight so her weight stayed the same for basically 3 months as she had to build it back up and was barely eating for about 2 weeks and had been bad before that due to various colds etc. All of a sudden she’s feeling better and eating loads more and the weight is finally coming back up so was just a (stressful) phase for us
A phase and can take a while for their appetite to return. I'd recommend a good stock based dish - soups, congee, pasta like Orzo or the little stars to help build up and then nutrient fat dense foods like avocado.
Once they are 1 they may start to eat a little less, their growth slows down. Did with my first and now second x