Carrots in buckets

This year I'm trying a few buckets full of carrots for the first time. I planted them up with a mixture of sharp sand and GP compost. Today I pulled some to eat as baby carrots, a few from each bucket, and every single one of them is gnarly and deformed. They're a mixture of Royal Chantenay and Chantenay Red Core.

What has caused this? OK, you do get the odd lump in GP compost, but it certainly isn't stones. Is it perhaps because the GP compost is a bit too rich?

Mmmm - surprised at that. Did you sow direct 'cos if you replanted them from, say, a seedling tray, that would damage the roots. Did you water tme well as they may have tried to put roots down in all directions for moisture.

Yes, I did sow direct in the buckets, and I water them every day because they're in the greenhouse (which has missing glass so it doesn't get too hot).

If the soil is not too rich I would say that it's the watering to bame.  Do you water from the bottom or top? 

From the top. They're quite deep buckets with just puncture holes in the bottom, and I suspect they'd have to be standing in pretty deep water for it to soak all the way up from the bottom. And given that there's 8 buckets on the go, I don't think I'd really have room in there for all of them to be standing in containers big enough to hold a decent amount of water. Maybe the answer is to take them out of the greenhouse and stick them outside. I didn't do that before because I was trying to protect them from my evil lurcher, who already dug up all my spuds in containers.