Question
yellowing leaves and purplish spots...the tree was absolutely beautiful a month ago...I cut it back to the fifth leaf and now I don't even have any buds.. most of the leaves are turning yellow..appreciate your help

Answer
Its a disease called black spot
yes its really black   maybe dark purplish spots prob caused due to high nitrogen fertilizer plus lots of water?

a few things
you need to feed it better
i guessing MGrow?  Not my fav, try any good organic rose fertilizer.
apply a small amount of compost mixed with equal amounts coffee grinds. add 1 cup of the organic fertilizer, 1 cup rock dust or gypsum, 2 tablspoons sugar, 2 tablespoon Epson salts,.
mix well together place around base of plant water in well.
Ok
heres the thing about watering.
I would get a garden filter  Try Garden Gro  see Google or http://www.amazon.com/Rainshowr-GG-2010-Garden-Filter-System/dp/B000N4K4H2/ref=s

Try not to over water, best to allow to dry in-between watering

you should spray the roses with seaweed
if you have access to compost, make compost tea and spray that twice a week

Milk is a good spray also, 1 part milk, 10 parts clean water

let me know if this helps