Why low profile? They are the worst when it comes to trying to keep heated cooler exhaust air separated from cooler intake air.. Same goes for your GPU cooler but will reserve that for somewhere else. A cooler is only as good as the air temperature feeding it. Not the room temperature.. the temperature of air actually going into coolers. Your GPU makes more heat than your CPU.. and is dumping all that heated air inside of case.. same as downflow coolers do.. and this is probably raising the temperature of cooler air intake by 5c or more.. that translates to cpu and GPU being 5c or more hotter.
Could you give us your case specs. Like what fans you are using, their location and running speed.. How tall is your RAM above motherboard.. and distance from motherboard to side cover.
And if possible the air temp in front of cooler fans while stress testing.. both CPU & GPU.. and room temperature too.
I use a cheapy digital indoor/outdoor thermometer
Warning: Spoiler! (Click to show)
cheap digital indoor/outdoor wired remote sensor thermometer with piece of stiff insulated wire twisted into the last 20cm of lead to remote sensor. A plastic clothespin and you can position sensor most anywhere to see what air temp is near components.