The solo commercial pilot was doing full stop night landings, to become night current under Title 14, CFR Part 91. He said on his third landing, he noticed that the vertical approach slope indicator (VASI) lights were becoming red over red indicating that he was below the glide slope. He said he should have applied full power. The pilot reported that the airplane continued to descend, and struck the elevated instrument landing system (ILS) runway centerline lights and terrain short of the runway. He said there were no mechanical problems with the airplane prior to the accident. The airplane's fuselage sustained substantial damage during the accident.