I'm guessing you want honest opinions........
1 - you're defeating the purpose of having dual 1" overflows by connecting them together into a 1" 'T' and additional 1" fittings. This restricts the two 1" pipes. There's a LOT of turbulence inside the 'T'.
Each 1" overflow can handle 600 gph, if there are no restrictions in the pipe. You have ball valves on the overflows, so even if those are wide open they do restrict the flow a bit.
More importantly, when you connect the two 1" pipes together, you basically reduce the capacity to 300 gph for each of the two overflows. You should have the two 1" overflows either running individually into your sump, or have them connected into a 1.5" pipe.
2 - Your return plumbing is probably not feeding both return outlets with the same amount of flow. There appears to be a lot of back pressure on the line that dips across your sump. Have you checked the flow from each of your return lines inside your tank?
I didn't intend to be critical. Hopefully this will help.
swimmer