question about my female festae

[belfiore11]

So I have a 125g with a male and a female festae. And for the past week she just hasn't been herself. Her color is dull her stripes arnt really there. She still has the hit of blueish black and light red but not vibrant colors from what she was. Whats wrong? I do 40% water changes every 2 weeks. Idk if shes stressed or what. Any advice would help thanks.!!!