Dimension font resizing to last edited dim style

I've had some problems with dimension fonts resizing to the last edited dim style. I have attached an example drawing. There are 2 styles here 'Gdims' and 'Stand Dims' The Gdims need to be small font and the Stand dims need to be larger. I have set the size of each style, but if I stretch the larger dimensions they auto resize the font to the set size of my last amended dim style (in this case GDims). You'll see in the attachment that I have resized the 2 blocks and the dimension font has become smaller than the rest.

Not all of my drawing behave in the same way so I'm assuming there's a setting I need to change, but as yet I haven't found it.

Any help would be greatly appreciated.