Half my terrarium fern is soggy and brown and the other half is green and soggy – how to save?

Hi horticultural heroes – my terrarium seems to be really struggling. It’s really soggy and the fern is brown and looks to be maybe dying. However the same fern in the other side of the jar is green and seems to be doing ok.

I planted this about 4 months ago. I will turn what side of the jar faces the window every few days. And yesterday I took the top off for about 5h to try and dry it out. What should I do to salvage it?

Thank you!