Sweat marks don't look right under saddle?

Those sweat marks do not indicate too narrow a saddle but instead too wide - there is concentrated pressure along the top edge of the panel, if the points were too narrow you'd have more pressure at the points themselves, also at the back of the saddle, and at least borderline bridging in the middle IF the tree shape is otherwise right for the horse. Don't put in a wider gullet without further advice (I'm happy to look at some photos of the saddle on if you can take some).

Oh and to help you explain what's going on better, the panels are the whole flocked/air bits, one each side. I suspect your saddle fitter was adding shims between the panels and the tree (I don't fit Wintecs but understand the modern ones have a shim system).
 
Just an update for those of you who want one :) I had a look at saddle and even to my untrained eye it was very very tight and she wasn't happy being tacked up for me to do a ride without a saddle pad on and so I got the next size gullet out and put it on her back as saddle fitter said this is better indicator than the wintec measure thing and next size up much better so I changed it and she went beautifully which she hasn't done the last few days when I noticed funny sweat patches she has been pretty grumpy if truth be told and not been so happy for me to mount and when I took saddle off much more even sweat patches so for now we are both happy thanks everyone for all your help!
 
Proceed with caution, you've potentially moved the pressure spots so she'll nbe happier temporarily. Just keep an eye on her, and I agree that you need to put the headplates in to see if they're correct, not just plonk them on on their own, the saddle needs to be girthed to assess tree width.
 
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