The thing is, if you're really good at Spanish (i.e: the language in general, by this I mean actually fluent in the language as opposed to just GCSE good at it) the workload shouldn't be too bad because your main priority would just be staying on top of all the essays you're given to write, making sure you complete all of them and ensuring that your exam skills are really good. However, if you aren't I'd drop one and stick to four- it's better to have AAAA or AAAB then AABBB or even ABBBB. The point is, it's best to focus on doing well in fewer subjects, I think the workload may be a little too much especially as you have Maths, Biology and Chemistry which are all subjects that A* GCSE students have even failed at simply as a result of not having enough time to study all the content etc.