The COB's should be doing a more efficient job of converting electricity to light, so should produce less heat per watt at the LED. Is the overall wattage of the light rig higher than that of the LED's? For example, if the COB's are 70 watts each, for a total of 140 and the old LED was only 100 watts total, that could account for it. The efficiency of the driver itself is another thing to lo .ok at. Most of the heat on my rig feels like it's actually at the driver.