drainage issues

my baby is having some drainage issues, using MG veggie mix soil ina 3 gal pot (largest i have) i just bought some perlite but i dont really know how to add it without ripping apart the existing roots. any suggestions?

It's best to dig 'em up just before you have to water.

well they're outside, due to weather conditions i havnt had to water in 3 weeks

Perlite gets added to the soil before you plant, not after. Save it for next year.

As long as the plant is still small / as in small for the pot

You could always dig it out like transplanting a plant from the ground to somewear else