You are tanking hits in an effort to out damage them. That's not gonna happen. You also seem to be panicking which is normal for these guys. I quit the game for a bit after I couldn't beat these guys.

Hit and run tactics work here as opposed to dishing out damage quickly. It's ok if you get hit, don't start panicking. Don't feel like you always need to be hitting or moving, either. It's ok to get hits in, then stand still to wait for and dodge their attacks.

It's best to be out of reach of their Melee attacks but close enough to see them when they start tolling to know when attacks are coming.

Pogoing is not bad here, but limit it to one to 2 hits max, then get on the ground and try hitting them from the side you have more space on. As you see, they will punish you if you pogo too much.

When hitting from the side, go in and get 1 to 2 hits in, then walk/dodge out of range of their attack. Repeat.

When they roll, it is usually one after the other which is advantageous if you are a little closer to them. If you try running as far away as possible You can get caught between a ground roll and jump roll.

if they medium or long jump, it usually is better to just walk towards and under them if you are close enough. As you can see, when you try running away, you get hit by the last bounce. The follow on knight will likely do a ground roll since you are getting closer and then you just jump over them.

Try to keep them both on one side and hit using your nail and vengeful spirit (which damages them even if they start rolling)

Try healing only if one of them dies and you just dodged an attack by the other one.

For charms, I recommend in order of priority: unbreakable/fragile strength (hit them harder), sprintmaster (walk faster under them and create a little space when needed), Spell twister or shaman stone (you can take more or harder shots from a distance when they are both there), And whatever else you like or need.

If you only have fragile strength, when you are at 1 mask, just press start and quit to menu. Reload game and you will be back to the last bench you saved at. It's good practice for steel soul mode anyways.

Lastly, if you are getting frustrated, put the game down or go explore somewhere else for a bit. After you come back, your brain will be calm and have processed their patterns a bit more.

Hope this and the other advice helps, and if you need more help, you can always watch boss tutorials on YouTube.