Astronomically low speeds

I am currently getting astronomically low speed whilst using one antenna (2.5ghz) as client and the other antenna (5ghz) as wifi. My current download speeds are over 30mbps since im using my router as a wireless bridge (cause max speed from ISP = 100mbps). Wired to my router i get around 30mbps but when connecting wireless i get 2mbps max, could it be some error in configuration?

What build of openwrt?
What router?
When you say antenna do you mean radio?
Is your wifi bridge to far away from your mane router? because if the signal cant reach then it will slow every thing down.

it's not how you think, you have a dual band device with two dualband antennas