Former world champion Amy Marren, 17, achieved the time in the SM9 200m medley.
Matt Wylie, 19, and Ryan Crouch, 22, met the S9 50m freestyle standard.
Sascha Kindred, aiming to reach his sixth Paralympic Games, missed out in the SM6 200m heats by 0.23 seconds. He races again in Wednesday's finals.
It takes the number of GB swimmers to have achieved the qualification times for Rio to 24.
While they are not guaranteed a place in the GB team for the Paralympics, which run from 7-18 September, they are highly likely to feature when it is named next month.
Three more swimmers achieved the Rio Paralympic qualifying standard at the British Para-swimming trials in Glasgow.