Triple rad, the best temperature I ever managed was bottom and side intake, top exhaust, rear exhaust, same order as yours (top rad exhaust most of the heat, then side and bottom (as intake and using fresh air will be able to drop the coolant temperature as low as possible, even if their exhaust is affecting the top rad, it's minimal).
Now, walking with a target on my back, tried to use 3 Corsair 30mm ones, and their performance was way worse than the EKs I was using. Clearly the XE at the bottom is a blessing, and 2 PE would keep even the 3090 at bay temperature-wise.
Not fair comparing 3 x 30mm rads vs 2 x 40mm + 1 x 60mm, but as you have a thick rad, something odd is happening.
The bottom rad is the only one I would bother going push/pull.
As the coolant is getting hot, I don't believe any issue with the mounting of the blocks.
The only thing that my be affecting your loop now is flow rate.
Non-EK fittings can affect the flow on the GPU block. Not your case. You're using EK fittings.
There's only 2 things I could suggest: the GPU inlet, despite allowing any side as intake, anyone knows what effect it has using one or another as inlet, regarding flow?
Another, the cheapest "solution" would get a flow meter. One thing I noticed with the Corsair rads, which are basically your rads under another skin, is they are very restrictive. No joking.
Dual D5, minimal angled fittings and was struggling to get past 180l/h.
As I mention on other threads, my delta was always around 8ish Celsius. Fans would go up to 1000/1100 rpm/ Faster than that, would defeat my objective for watercooling (low noise). But the 3900x doesn't get as hot as some 5000 series, and during gaming I'm not really pushing the CPU.
