Unhappy crocosmia

Last year I was given some crocosmia plants direct from a friend's garden. One got planted straight into a clean tyre, the rest went into various little pots as I didn't have anything else to put them in at the time. This year one of the others has gone into another tyre, after a year of staying very small and miserable in its little pot.

The second picture is the one that was planted in the tyre last year, the first is the one that went in earlier this year. They come from the same plant stock in the same flowerbed, same compost in each, the tyres are the same size and were both cleaned and thoroughly rinsed before use, and I have been diligently steering my dogs away from them :P The only difference is that the first one had a bit of garden soil mixed with the compost (about 50/50) as I didn't have much at the time. Would that be enough to do this, even though it came out of plain soil to start with?

I fed the unhappy one a couple of weeks ago with miracle gro, and it got a couple of feeds late last summer too until it started to die back in autumn. Why is it looking so bad? I've had crocosmia for years out the garden and it's always come back well each spring, at least until the nettles overtook everything this year! Do I just need to feed it more? It doesn't dry out nor is it overwatered. The happier one isn't as bushy because it had some weeds competing with it so it's not grown as much at the back.

 

I may be wrong here, but, usually when I see bulbous plants looking like this I think it's because they're too dry, or, have been allowed to dry out at some point.

 

To me they look rather crowded in the tyres. I would certainly recommend mixing some garden soil in with the compost or repot them into John Innes 2 or 3 and reduce the number of bulbs, in each tyre, by about a half they will soon bulk up again and fill the tyres.