What/How should i feed my horses with special needs

Im in a dilema. I have two horses that are boarded together in the same pasture. I have a 20ish TB gelding, and a Percheron Paint cross. My tb is extreamly difficult to keep weight on, and broke his hip last year, so he is not getting excerise, but is able to roam his pasture. My percheron girl is an easy keeper, and is riden on the trails a few hours a week. My problem is, what should I feed my tb that my percheron can also eat, so he gains weight. They are currently getting 2 flakes of triple mix morning and night. Is this enough? My tb boy is still thin, while my percheron girl looks great.

Thanks for reading, this is my first post, and id love to be more active!

You need to separate them at feeding time so you can give the TB what he needs without endanger the Perc cross from foundering

I would increase the hay a little and like PeggySue said, separate them for "feed." I'd put your TB girl on a quality Senior feed like Triple Crown's or Progressive's. Feed at the bag's recommendation.
Triple Crown Senior Formula | www.triplecrownfeed.com
Premium - Senior Formula

ADM's SeniorGlo is also a very good product.
http://www.admani.com/AllianceEquine...OHorseFeed.htm

A few other good senior feeds. Check the dealer locator to see what's available in your area.
http://www.seminolefeed.com/seminole...sSeniorMix.pdf - Another great feed, high in fat.
Pleasure/Leisure - BUCKEYE® Nutrition

I would avoid Nutrena or Purina Senior feeds, or Dumor feeds. These three are lower quality.

These types of products would be good for your Percheron mare, to make sure she's getting all of the vitamins and minerals she needs, without making her too fat.
Seminole Equalizer - Ration Balancer for horses
StaySTRONG low starch mineral feed supplement
Triple Crown 30% Supplement | www.triplecrownfeed.com
Gro 'n Win - BUCKEYE® Nutrition
ProAdvantage Grass Formula