Rose buds not opening

I’m having a problem with one of my roses. It’s a David Austin, Gertrude Jekyll English rose and although I have lots of buds on the shrub, they appear to be going brown, the petals look like they become deformed and as it begins to open I can see it’s brown and dying inside. I’ve had it since last year in the pot I got it in and it flowered beautifully up until I put it in the ground at the end of April this year. I have other David Austin roses that I planted in the same soil at the same time and they’re all producing big healthy blooms. If this is a pest, is there a companion plant I can use to help it? If it is something else, is there a natural solution, I’m really trying to avoid chemicals.