the first pic is what i think is the graft line and heres the new bud thats starting just above the soil

Rub off that bud; you are correct about the bud union; and anything below that is rootstock. Without seeing the whole tree, I could be wrong; but it sounds like your tree is a goner; if you wait a few weeks it could come back.
I would guess it is not a root problem; because the root is trying to put out new growth.
You say you flushed the soil; but it still looks like a salt buildup there; are you by any chance watering it with water from a water softener?

heres the photo of the whole tree, its hard to tell but the branches are all a dark dark brown almost black. they were green at first which is why i cut them back in hope of new growth but they just turn brown as well.

for the water softener i have no idea. would that be something i add or the water treatment plant in my area, or could it be something the building adds before the water comes in? i could do some research and find out, we just moved in here about 2 months ago so it is possible the water could be causing it.

and i never seen signs of salt build up as far as browning tips on leaves or anything, just that all the leaves dropped and the branches turned dark brown. i wasn't home to witness the leaves before they fell :/ i just assumed something in her solution was causing it so to be sure i flushed it, it was the only thing i could think of to try and revive the plant and more a safety precaution (figured it couldn't hurt to try)

It looks like you have a bud union failure; and maybe an interstock. Looks like there is a second bud union higher up from the first one you identified. If it were mine I would dump it and start with a new tree.
As for the water softener, that is almost always something you would install; and you would know you have it, because it needs regular maintenance.

alright ill do that then, thanks for the advice.

ill also test the water ph just to be sure . do you think that might have caused the problem?

is that normal to have 2 bud unions? when you say bud union failure what exactly could have happened to cause this if the tree was already thriving?

2 bud unions means there is a rootstock; and another variety grafted to that (called an interstock); and finally your mandarin grafted to that. It is sometimes done because your variety is not compatible with the rootstock (maybe a dwarfing type); so they have to graft a compatible citrus first and then the end product. It could also mean that they just grafted your mandarin onto an existing tree. Interstocks are often sensitive to failure which could be caused by a virus in one of the three that blocks the flow of water and nutrients. Maybe that is more than you wanted to know; but in the end it is probably the nursery's fault and not the gf. LOL

haha i dont blame her anyways I'm just thankful she waters them for me :P
but thats good to know now i don't feel so bad about the tree dieing.
does the risk of that happening lessen as the tree gets older or is it always gonna be a weak spot in the genetics that ill have to worry about? I'm just asking before i go out and get another mandarin tree and have the same thing happen 6 months down the road :P

and if this is a virus is it contagious to my other trees as well? and if its cought early enough is there a way to fight it/ prevent it all together?

I would not buy a tree with an interstock; the three varieties grow at different rates; and although the failure usually occurs while the tree is young, there is always a risk. As for the virus, if it was in one of the three trunk materials, there is no way to prevent it; it is not contagious to the other trees in all likelihood. IMHO you are always better off buying trees from a reputable nursery; and not from Home Depot or the other big box stores. As a grower, I can assure you that those type sellers would never get my premium trees... perhaps some that were lesser quality or hard to sell.
The other advantage is that a nurseryman can give you advice on what variety and rootstock would be best for your conditions; and also would replace the tree if there was a defect.

okey that makes sense. thanks a lot for the advice its unfortunate to loose my tree but at least I've learned from the experience. normally your right about buying from big box stores but in this case when i seen the tree and how poorly it was cared for there i attempted a rescue mission, and the tree was doing lovely great until we moved :/
its to bad. also you can't beat the price at those bigger stores. the nursery that supplied the tree was the same one i seen at the garden centre but the tree at the garden centre was around 95$ vs 30$ at home depot. regardless... lesson learned ;)
thanks again
chris

john would you mind if i emailed you with some questions i had. you got me thinking on the whole water softener topic and ph of my water, its a little off topic from this thread and i didn't want to start a new thread for that in the citrus forum.

CLM... sure, lots of people email me with questions.

John

Chris, you can get perfectly good citrus at the big stores, just don't do any rescue missions. I did one last year and the tree promptly died. My fault, I knew it was in bad shape! It's been replaced with a healthy one that's doing great.