The motherboard manual quotes a maximum 1 Amp (@12V) load for the CPU fan header but, nothing is quoted for the chassis fan headers although I would expect they are the same. The fan spec quotes a maximum load of 0.3A for the fans, so I should think you will be OK using splitters for two fans per header. Cannot guarantee that though. If it is not OK the only consequence likely is the the fans may run a little slower than intended.
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