Let me guess, the card in question is EVGA or Gigabyte and the second one is another brand? Most likely thermal throttling is the case, 3080\3090 are known for that, these 2 brands being the worst (in that case only LOL). Note: it's not the core temp that you see in afterburner, it's memory temp, you'd need utility called HWinFO64 to see it. Download it, take a look at your memory jusction temp sensor reading and you'll most likely see 110-112 degrees Celsius. Common fix is to change thermal pads to good quality ones with 12-17 W/mk (I use these, https://cdn.alzashop.com/ImgW.ashx?fd=f4&cd=CB131w1&i=1.jpg) and do everything possible to improve  the ventilation.