Schottky dfiodes rated up to 40 volts PIV drop as low as ,45 volts. You did not say half wave or bridge rectifier and this makes all the difference. So, what do you have?
In a bridge rectifier voltage goes thru two diodes at same time, thus 1.5 volt drop is normal. 1 amp diodes carry 2 amps in a bridge with your rectifier. 3 amps is not good in a bridge. So, change out to 2 or 3 amp schottky in a bridge rectifier and get under a volt drop.
If half wave rectifier, use at least a 3 amp schottky diode for lower voltage drop.