When the window is created SDL_WINDOW_FULLSCREEN_DESKTOP, and focus is lost and restored any alpha blending is lost on the texture.

Here is the object's constructor that sets the alpha blend:

Bubble(SDL_Point pt, int radi, Uint32 format, SDL_Color clr, SDL_Renderer* render)
	{
		Circle* circle = new Circle();
		circle->Set_Radi(radi);
		circle->Set_X(pt.x);
		circle->Set_Y(pt.y);
		area.x = pt.x;
		area.y = pt.y;
		prec_area = circle;
		Img = RenderCircle_Fill(radi, clr, format, render); //Draws a circle
		SDL_SetTextureAlphaMod(Img, 100); //This works until loss of focus
		Recalibrate();
		popped = false;
		alive = true;
		up = rand() % 15 + 5;
	}
To my knowledge, any texture works with this issue. When in fullscreen, use Alt + tab to see the issue.