Agreed. 60% is too high. They prob drowned. Styrofoam bators are ok, as some are better. U should monitor the temp in various locations: top, bottom, center, outer edge. It takes a while to get the temp right. I often put water in two ziplock bags and a thermometer in between the two. Supposed to mimic the internal egg temp. The temp at the Egg top should not get above 102.
As u've found out, ALWAYS do not invest in expensive eggs, till u perfect your hatching technique. Research dry incubating. Works for me, but I prob depends on where u live. Here my humidity is 20-30 without adding water. I've done the buying expensive eggs and failing too, but I've also had good hatches. Trial and error, I'd say