YAY for poo, yay for poo
!!! Oh, what a relief!!! Well, you could go a couple more days of potato/chicken if you like (adding in more chicken now). But, what was she eating before this and what is your long term plan for her diet? Kibble? Canned? Cooking? Raw? Since the current diet isn't truly balanced, you don't want her eating this way too long or there will be other problems
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If she needs to be on a weight gain diet, there are plenty of things you could add to any diet you choose - like peanut butter, bits of cheese (depending), little bit of olive oil (depending), supplemental meats. If you feed kibble, you can also add in canned food to supplement her. Feeding raw is very dense, so it doesn't take a lot of volume for calories. And if you cook, there are a ton of options there - you just really need to be sure you're balancing the cal-phos ratio etcetera.