Help with my hydrangeas!

Can anyone tell me where I have gone wrong with my hydrangeas? One has grown big, with dark leaves and flowers and the other three have barely grown and are really pale in colour. They were all smaller versions of the big bushy plant when I bought them last year. They were all planted in the same pots, compost and deadheaded the same. they were also positioned in the same spot until recently so had the same amount of light and water. I am mystified. Any advice would be much appreciated. Thanks

 

I take it they are different varieties?

The yellow looking ones look like they want to be blue flowers but are growing in normal compost, so coming out pinkish, they appear to be suffering from chlorosis.

Are you feeding them?

 

Thanks for your reply.

when I bought them, they all looked the same and had pink and purple flowers and dark green leaves.

I haven’t been feeding them so I will start doing that and see if that helps.
Thanks