Just a thought, but your results would pretty much exactly as you've measured if you had misconnected the fets.
Looking at the base of the fet, with the leads pointing towards you, and with the flattened side uppermost, the gate is the lead on the right (left to right would be: drain - source - gate).
If you find you have got them wired up wrongly, it's possible you may have damaged the fets, so it would be best to replace them (correctly connected!).
Of course, the above hypothesis may be completely wrong!
Looking at the base of the fet, with the leads pointing towards you, and with the flattened side uppermost, the gate is the lead on the right (left to right would be: drain - source - gate).
If you find you have got them wired up wrongly, it's possible you may have damaged the fets, so it would be best to replace them (correctly connected!).
Of course, the above hypothesis may be completely wrong!