Yes, both Horse need some weigh and muscle tone, the Horse with the white mane might be able to use the English Saddle one day. Nor sure about the other Horse.
The last Saddle is too narrow, but again a lot of weight and muscle tone is needed, but this would make the last Saddle fit worse.
I can only Guess, the English is a Wide and the last Saddle is a Narrow or Medium
Maybe a medium-wide for the Horse with White mane, nothing would work for the other Horse at this moment that I can think of.
When fitting a Saddle you want the Bar of the Tree in the Saddle to have the same angle to match your Horse, so the Top of the Bar and Bottom of the Bar make the same amount of contact (pressure) form top to bottom.
On a Western Style Saddle you can feel the Bar under the Fleece, the Bar is about 3.5" Tall and runs the lenth of the saddle from from to back, as the majority of the weigh is on the Front of the Bar, fitting the wither area is the MOST important.....
May all your Trails be happy and safe ones