Recently Bought Baby Chicks And Ducks. I Was Told To Keep Heat Lamp On Unless Temp Was Above 90's. Had A Heat Wave, Turned Off Light. Night Temp - 60's, Day - 80's. Can I Keep Light Off Now?

First if they are younger then 6 weeks old they should have the starting temp dropped by 5degrees after each week. So started at 90 days old, dropped down 5 each week. If the temp is 60 at night that will be a little cold for young hens and they don't need the lamp at all during the day due to it being 80 or higher. So keep the lamp on at night til they have become of age. Also when they do mature to with go the lamp at night its still a good idea to keep a temp. Gauge to ensure they have a good amount of warmth. They will need it at night of course if the weather is rainy and cool to. Keep them dry is the key, so if they do get wet they have something to keep their bodies warm because the water will make their body temp drop also. Also when the weather changes to colder nights and days the lamp is necessary

You do not really want to go cold turkey with the heat lamp.  Your best bet is to lower the temperature by 5 degrees each week to prepare them for the outdoor temperature.  Then it will not be a shock to their system when they are outside without a heat lamp to keep them warm.