HELP...WINDMILL PALM SCALE

Hi,
I am both new to the forum and to gardening!!! I purchased 3 Trachycarpus fortunei palms. Two are doing very well indeed but the third has what i think is palm scale. I can only describe that the poorly palm has clear like dots which have a brown centre. When i have removed them they kinda go orange but the palm leaf is left yellow. There are loads of these spots on both the underside and top of the fronds. They are also where the stem joins the trunk and on two new emerging fronds. I have spent ages with tweezers and treated with scale spray from b & q, whilst this helped Ive noticed that the spots are starting to reappear. Does this sound like palm scale and can anyone recommend any treatment. Or should I cut my losses and get rid of the plant. I am particularly worried that this might spread to my other two. I have nagged my partner for years to have a jungle garden and he's finally relented and this happens Any advice would be truly appreciated. Michele.