So, we seemingly had two very similar penalty incidents in the first game with different results (apart from not being scored) - one was a red card, one wasn't. The rule reads quite strange.
Where a player commits an offence against an opponent within their own penalty area which denies an opponent an obvious goal-scoring opportunity and the referee awards a penalty kick, the offending player is cautioned unless:
The offence is holding, pulling or pushing or
The offending player does not attempt to play the ball or there is no possibility for the player making the challenge to play the ball or
The offence is one which is punishable by a red card wherever it occurs on the field of play (e.g. serious foul play, violent conduct etc.)
In all the above circumstances the player is sent off.
So if you bring somebody down by slide tackling them, as long as it isn't deemed violent conduct, that's a yellow. If you pull somebody back or simply push them, then that's a red.
So perhaps the refs got these right. Stalybridge was a foul, Tamworth was a push.