You have no fixed starting time for your one minute interval.
minutos was set = millis() at startup. Then you must take some time to program alarms[alr] to the value of 1, since they are initialized to 0.
Depending on the time you take, the current value of millis() the expression (millis()-minutos)/60000 can be only a few milliseconds from being ==1
To check this out, either set the values of the alarms to 1 in setup and don't adjust with the button, or set minutos = millis() at the end of programa().