Hi BherrO, welcome to the forum! 
I do not believe your fish died to high PH. Goldfish can adapt to a wide range of PH. You should not have messed with the PH level. I am also curious. Did you use some kind of chemical "PH up" and "PH down" products to adjust your water PH? It is a big no no here. Messing with water PH in your aquarium will cause more harm than good. These products can change the PH suddenly, which is exactly what we need to avoid. Fish can be in shock or even get killed by sudden large change of PH. Stable PH is not a problem even if it is higher or lower than their ideal environment.
By the way, your fish tanks are not big enough for two goldfish each. Fancy goldfish requires minimal 20-gallon for the first one, and total 30-gallon for just two. Common goldfish requires 40-gallon for the first one, and total 55-gallon for just two. Neither of your fish tanks is big enough for the minimal requirement.
I'd also like to know what kind of aquarium filter you are using.
More fish are killed by ammonia poisoning than anything else. Sufficient biological filtration is needed for their survival.
If you have the time, please check out our article of Why did My Fish Die. It might give you some insight on the actual reasons for your fish dying. 
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