All of the leaves on most of the stems on one of my dicentra spectabilis
are yellow with green flecks whilst the leaves on a few of its stems are
perfectly normal. Otherise it is a normal healthy plant with an
abundance of flowers.

Before I treat it for magnesium deficiency, does anyone know of a more
likely cause and if so the appropriate treatment.

Thanks.
Regards
Emrys Davies.