Hello Ika,

cause you have 2 extenders, may I know how do you connect them together? In other word, what is the current network topology/network diagram?

Besides, you can refer  to the information below to troubleshoot. https://www.tp-link.com/en/faq-2232.html and we need more details to do further analysis.

1. The speed you can get from each extender and main router.

2. The current light status of the extender.

3. The distance between each other and the signal strength.

4. Please check the wireless link speed with your device connected to the extender. https://www.tp-link.com/en/faq-2265.html

5. To do a comparison analysis, please put your computer next to the extender and connect it to the main router to run the speed test and show us the result. 

Thanks for your cooperation. 

Good day.