Allotments 4 All

Help, my blackcurrant bushes all have these reddish brown patches on the leaves. Please does anyone know what it  is and what I can do, or what have I done to deserve this.   :'(

I think you will find it is an  blister aphid XX Jeannine

A photo would be useful, if you could post a picture of the top side and underside of an affected leaf.