Electrical question please help

I have large grow tent with 2 air cooled 600W hps, and 250watts of side lighting. Plus 300 watts of ventilation. (fans, intake, exhaust, light cooling).

So altogether i have about 1800 watts im using.

I have this load spread across 3 outlets. 1 light per outlet and the fans and side lighting on the 3rd.

However yesterday my power tripped. And all 3 outlets went out along with a few downstairs.

I was under the impression that all outlets were on there own 15amp circuit. so im not sure why they all tripped at the same time.

My question is can i use a kill-a-watt to tell me how much available power each outlet has?

For instance lets say on one outlet i plug in 5 amps of power would the other outlet about 8 feet to the left only have 10 amps available?

Can a kill-a-watt tell me this?

everything that tripped is on the same breaker

if you have electrical experience you can locate thewires leading to the three out lets in the breaker box and put them on their own breaker. there is usually space for a few more breakers