I agree, poor little plant. Fingers crossed.
The older leaves not only look very sick they also look a bit shiny on the backs as well - I suspect they have been sprayed with some sort of leaf gloss as well as whatever is going on... over watering or underwatering.
I would chop off all those dying leaves, they will not recover and currently are just drawing energy away for no reason.
You say you repotted it - please describe what you did?
I can see the new shoot(s) which is hopeful. I have no idea what that scoria on top comprises. The bottom pot is solid so what's the drainage situation? Please take the brown pot out of the white pot and make sure it can drain properly while you put it in "plant hospital" somewhere in bright light with no drafts. Check for any sign of insect infestation - mealies/spider mite that might have been contributing to its sadness. Don't overwater it and if you have already incorporated some fertilizer, don't give it any more for a bit.

Thanks for the respond alisonoz!
There is no leaf gloss on it, I just sprayed with some water before I decided to take a photo and ask for help on the forum.
When I took her home, I was at the beginning of an experiment with houseplants in semi-hydro, so she had the roots somewhat trimmed (root system was quite healthy) and repotted to only clay balls in the pot.
The old soil was a good quality well-draining one only nobody watered the poor thing and it was bone dry.
There are no insects, already checked in store and regularly since then.
It is sitting beside a south-facing window and gets indirect light. I am in Ireland so no scorching sun. My Calathea zebrina loves that spot so I thought it's gonna be fine.
Here is a closer picture about the shoots, there are about 10 of them. Maybe it took twice as long for her to adjust to semi-hydro than my other plants (they showed signs of new growth 3-4 weeks after repotting). They all got 1/4 strength fertilizer in the past month and am planning to change it to 1/2 strength.
So you still recommend to chop the brown leaves off? I don't want to kill her when finally there is some hope :)

Calatheas are known for their fussiness. I believe what happened was it experienced stress from being allowed to go bone dry and I'm assuming you repotted it soon after purchase (trimming the roots wasn't a bad thing nor was repotting, but it may have also added to the stress level this plant was experiencing). They don't want wet feet, but they don't want to dry out completely either. Whatever you're doing with the clay pebbles seems to be working.

That being said, it's obviously making a comeback with all those new shoots (they will turn into new "plants," still attached to "Mama," but a plant of its own).

I'd just allow the leaves to die on their own. When they're dead, then cut them. That way you're not worrying about stressing it out and it could still be using those leaves to produce food (if they're still green on them, the plant is using them).

They require high humidity, so what has worked for me (I have a Maranta, but they're related) is a big pebble tray that's full of water. That's all I do. But, everyone has a different school of thought and perhaps you will find something that works for you more. I believe the best option is a humidifier (but I don't have the money for that for one plant) and the least helpful thing is spraying it, the humidity only lasts as long as the water is on the plant/evaporating, then poof it's gone.

Planto

This post was edited by plantomaniac08 on Tue, May 13, 14 at 7:56

Thanks Planto,
a humidifier is quite expensive, I'd rather go for the pebble tray..

Sounds good to me. :) I meant to say that my pebble tray is a plastic tray filled with pebbles and full of water (not just a plastic tray full of water!) Give us an update to how it's doing in a couple months!

Planto

Yesterday all the leaves were crisp dry so I cut them off.
I really hope these shoots survive. For better humidity the pot goes in a clear plastic bag until the leaves unfold or something happens...

I'm sure that they will survive. When you do decide to remove the plastic bag, do so over a period of time (you don't want them going from a good bit of humidity to zip overnight). Maybe open the bag a little bit at first, the next day a little more, until you end up removing them completely.

Planto

I'm back with good news, the plant is doing fine!
Just don't know why the tips of some of the leaves are a little dry. Only the first 3, the rest are healthy...