As this is a push pull forward converter, there will need to be a pair of chokes fitted between the + and - outputs of the main bridge rectifier and the filter capacitors. The auxiliary supply also needs a choke.
That is, C1, C2, and C3 should each be fed by a choke.
Without these chokes there is nothing to limit the turn on current of the switching mosfets. These chokes are an extremely important part for the correct functioning of any forward converter, and cannot be omitted.