Is my horse at a dangerous weight?

I have a 7 year old arab maiden mare she is 14.2 hands and 684lbs weighed today she has put on 22lbs in 2 weeks and I really worked hard to help her gain that I have no grass that really grows here but 24/7 hay I have recently took her from 6/10 sweet feed to 10/10 also with a weight booster that has 25% fat hopeing that works would like to know sugestions of other things to help she is current on wormer I also got safeguard wormer and did it again today just in case 3 weeks ago the one i used did not clear all the worms I also had her teeth floated a month ago....