Default Wifi Issue---Slow speed

Hi

I am experiencing very poor wifi performance on my xperia z1 compact.

I am always able to connect to my router and all my other devices all work fine without any issues. The issue is that 99% of the time I am getting very poor wifi speeds (I am getting good signal to the routers wifi). The strange thing is that everytime I use the speedtest app, I am reaching my target speeds (around 16mb generally), however when I try to use other apps, I am getting extremely poor wifi speeds. I have tried a factory reset and also a repair using the pc software but i am still stuck with this problem.

I had been using kitkat 4.4.2, I was hoping that updating to 4.4.4 would fix this issue but it still persists. This is my first sony device, can somebody please help remedy this problem!