ESC calibrating for BLDC motors

Hello, I hope I am asking in a right place, because I don't know where to ask it.
So about two months ago I bought four ESC - "Hobbywing 20A ESC Skywalker Brushless Speed Controller BEC for 4 axis aircraft" from Ebay. I am trying to build a quadcopter with Arduino. So I reset everyone of them to factory settings. I arms them with 2ms of high signal and with 0.7ms with low signal.
I am using 1900kV motors. But when I want to start the motors on every ESC they start with different values and I think with different motor speed, don't know how to measure the speed but it sounds like they are different. So one ESC start motor with 0.85 ms othen with 0.75ms other with 0.72ms. Question how to make them all work the same on same speed, or I bought bad ESC's ?

Sorry for my english.

They are cheap, they are likely just standard ESCs not designed for quadcopters at all -
marketing claims on eBay should be taken with quite a large pinch of salt.

It may not matter - you can calibrate the idle/start level for each one once and live with
it - the dynamic performance under PID loop control is more important - if they don't
respond well to that you have a bigger problem.

Specialist forums for multicopters may have a lot more expertese on hand than here,
note.

In which forum I should search for help? Problem is that they all start at different ms pulses and I don't know if they have the same speed, I think not. If I calibrate them that highest position is 2ms and lowest 0.7ms should they start all at the same time and havethe same speed ?