The 2nd picture of your braces is not as clear as your pre-treatment photo so I will have to make some assumptions.
In your pre-treatment photo, it appears there is some minor crowding of the upper teeth. Your lower teeth are not visible. The lower (front) teeth may have started to protrude and crowd forward along with the upper front teeth.
I am not sure if you had any extractions done during your first or 2nd treatment. Some patients who have had extractions may feel that their tongue may be overcrowded or that their facial profile is becoming more flat.
If no extractions have been done, most of the correction that would have occurred would be through a combination of increased protrusion of the upper and lower front teeth and expansion of the arches (widening of the smile). This sounds like the reverse of what you are experiencing (sinking of the facial profile inwards).
I do not think that changing bracket type or brand makes much of a difference. Perhaps after the brackets were changed and a softer wire was used, the increased mobility of your teeth after starting braces can cause them to drift and open up diastemas where there were none previously.
Theoretically, it should be possible to reverse the effects of braces and return your previous archform without the crowding. This would have to be assessed from your pre-treatment models. If you were on Invisalign, reversing treatment is technically possible, but I have not yet seen any case reports attempting this.
Another factor that we cannot account for is your continued facial growth and facial ageing which continues throughout adulthood. These may also independently contribute to the changes that you have observed.
