Fish often die in new ponds, I would have waited three weeks not three days...It needs to cycle

Have you tested ammonia and nitrite? If not, please do so. I'm not sure I understand your time line. Is it now 4 days since 10-15 fish died? Have no more fish died? If so, you probably lost sick fish.

The temperature is pretty low, if they went from 75F to

Feeder fish often die quickly. They aren't often treated well and aren't all that healthy to begin with. They are food. If you have that many survivors you have had pretty good luck.

Thanks all!

what is the ideal ammonia and nitrite reading?

First off NEVER put feeder fish in a pond. They are often diseased and shipped in too small of containers, introducing yet more fish disease. I would sell the feeders back or put them in a tank and remove all the water and begin again. I have worked extensively with feeder fish and every morning we'd scoop out 20 dead or dying out of the 300 they raise in a 10 gallon tank. I have a Water Gardening book coming out soon, so that may help. Also I'd get the complete test kit as mentioned above. BTW if you have any lotus or water lily's to trade, I am volunteering to plant them at our new park. TY!

Here is a link that might be useful: FB

The only safe levels of ammonia and nitrite are zero.