[rfeenstra]

Your 5X4 may be tired.  Or, you have something else drawing too much current.  The biggest power suckers are going to be the 6L6's.  Make sure the grid bias is ok.  Given your -54 volts at one end of resistor 115, you should see about -21 volts at the junction of 115 and 116.  This supplies the bias for the grids of the 6L6's and about -20 volts on the grids should be good.  If they get too close to 0 volts, the tubes will draw too much current.

What is the voltage on cap 70B?  this voltage supplies the driver plate through the driver transformer. Does the primary of the transformer measure around 400 ohms?

Also, check the candohm resistor 117. These are often bad.