When you focus on one chakra, how much you feel it? How much you feel it's shape? The more you feel it, the stronger it is, and I do not mean feeling it as a pressure, it is like feeling them as your limbs, like you are sure they are there and you can control them.
For the lower chakras they might be harder to feel but you can test if they funcion correctly.
If this doesn't work:
https://ancient-forums.com/threads/raising-the-life-force-breathing-technique.302108/
Your base chakra doesn't funcion properly. The better it works the stronger it is.
For your sacral and sun chakra, see what they govern and how they are in your life.
Also, all of these has to do with purity as well, a chakra cannot be powerful or cannot work properly if not clean.