Wow. That's too bad.
I don't know much about riding Saddlebreds. I mean, I used to one one but she was used for fine harness back in her day and then I used her for english and jumping.
Anyways, there's quite a bit of things that changed that are causing her to get worse with her training. First would definitely having no say in her shoeing and what's going on as well as the not having the chiropractor coming out anymore, especially when she really depended on it. Secondly was having the part-time training dwindling down to no work done by that trainer. Now you are having to work with her.
May I ask why you even sent her to part training by someone else? Do you not have enough time to work with her? If she was going so well before hand, why the switch? I can understand moving her to another barn but to have someone else work on her can be a big mistake. Was the trainer reputable?
Opportunity is missed by most people because it is dressed in overalls and looks like work. ~Thomas Edison