Only have hot water when all faucets are on

Hi everyone obviously I am new here and need some help. Yesterday I installed a electric water heater. Now I can only get hot water from the sink in the bedroom bath when all the hot faucets in the house are on. The bedroom bath is closest to the heater, if no faucets are on the hot water comes out luke warm then cold.he main bath and kitchen hot only come out cold. The flex hose coming out of the tank is warm but any piping after the flex hose isn't. Thank you for any respones

Did you turn the electricity on before the tank was 100% full? If you did, it is likely you burned the upper element out.

Gary thank you for the reply. After I went back and pulled every thing off i realized I didn't take out the rubber inserts to keep debri out of the tank. Now every faucet gets hot water when it should. Thanks again for the help.