What can I do to make my Calatheas happy again?

I filter the water but maybe I should let the water sit for few days? I water them 2 times per week. I have now some fertilizer sticks as I never used those, but thought maybe it can help and should ask first here as well. unsure what's the problem 🥺 they do get indirect light from the windows but perhaps the lightning should be stronger and closer to the window but then that would be direct light..