A clip-on fan from an office supply store will go a long way towards lowering the temp. I'm sure there is a bacterial infection by now, which you should treat, but the cause of the infection might be an immune system compromised by inadequate diet, stress, and/or high tank temps. Yes, in the wild seahorses are exposed to higher temps than the low 70s, but in home aquariums, the higher the temperature of the tank, the greater the chance your seahorse will show symptoms of infection. This is what many people have observed, so do try to get the temp down.