Help! How do I rescue this plant??

[Planterlifer]

I have a plant that went from looking ok to quite suddenly being close to dead. Any advice please on how to revive it?
I think I overwatered it.
I have repotted it in a slightly bigger pot and given it some plant food. Other suggestions gratefully accepted

Don't give it any more food. A sick plant can't use it.

How long have you had it, and where were you keeping it?

Thanks @verypeckish
I've had it years and never had to do much with it.
I had it on the kitchen windowsill so it was getting light. It hasn't been too warm here recently though. I've moved it to a shadier room in the last 2 days in case it was getting too much light