Posted: 03/05/2016 at 15:50
From looking at the picture's the top dahlia shoot has died, the ones in your second picture look fine. I'd hazard a guess you've planted them on their side. Dahlias like a roomy pot, 12 inch pots are the usual for more mature tubers, which can be large, but smaller pots are OK, just as long as you can bury the tubers with compost. Some of what bought mightt have withered or failed, dahlia tubers need to be firm to grow well. Soaking newly bought tubers can help with this. Sometimes what you buy will be duff. If you use the search box and search dahlia planting, there's a short tutorial there on correct planting. It should give you an idea if you've gone wrong, not that it matters. You must have done something right to get growth so don't be disappointed. There is a lot more to tell, but watch the video see if you've gone wrong as that may be the root of your problems.