Can't Adjust Leading in InDesign (CC 2015)

Hello,

I've seen a few people with this problem, but none of the solutions I've found have worked for me. I have a text box with a single sentence written using different typefaces and sizes. See below:

I want to move the top text down to the edge of the rectangle frame box so that the space between 'Win a' and '€250' is the same as '€250' and 'Voucher'. But it won't budge. If I select all the text I can alter the leading no problem. If I select 'voucher' on it's own, I can adjust it's leading no problem. If I select '€250', I can make the leading bigger, but not smaller. But 'Win a' will not move either way. It's not a case of the paragraph symbol being a different size to the text. I've already found that solution and it failed to fix my problem. The text is not aligned to a baseline grid, and the text box is not is set to 'top' and not 'justify'. I've encountered this problem before, but this is the first time it's bothered me enough to make me actively look for a solution. I really can't understand why one piece of text won't move, one will move limitedly, and the other can be adjusted with ease. Any suggestions?

Thank you in advance for your help!