There is so much burnt flux on the board I would say it's the likeliest culprit. It might even be conductive, if not an actual short. The other possibility is that you have removed the board from the etchant too early, and it is actually still conductive in small spots. Try using a little less heat that way you will not scorch the laminate, and water soluble, flux cored solder. Thoroughly scrub your boards after soldering in warm water to remove all traces of flux, dry the board completely, then very carefully inspect all joints for shorts, splashes, and cold joints. Make sure discreet components like diodes, capacitors transistors etc are oriented the right way round. Only then power the board up and measure your supplies and if everything looks fine on the volt meter, then power down and fit your chips etc. Best way to avoid letting out the magic smoke...
rgds