Richardson System Piping

Back again with some further info on my system, a Richardson which is 2pipe vapor/vac with one main vent, radiators have graduated valves with els with ball cock for traps.  The original set-up had 11 rads, on 2 loops, however, there were 2 add-ons, a kitchen which has 2 rads with traditional packless valve and traps, and bath with same set-up.  The kitchen has it's own run of about 25 ft off main and is vented by Maid'o mist vent at end of air return; the bath was piped into main loop which now has 8 rads, 7 of which are original Richardson's, however one had valve removed and replaced by packed valve.  Other original loop has 4 original rads vented by Gorton #1.  Radiation load to each loop is as follows: origial with 8 rads 234 sf, original with 4 rads 144sf and add-on 140 sf.  Occasionally 2 of rads in 8 rad loop don't heat, do you think more vent is needed as line is not vented specifically, rather depends on main vent which is Gorton #2?  I will be adding vaporstat with low pressure gauge.