[golfdesigner]

Here's my run at your play.
I think you are describing two fouls on the same team (A) the offense. This isn't a double foul, it's a multiple foul. You have illegal formation (IF) on A, and you have either a personal foul (PF) on A or an unsportsmanlike conduct (USC) on A.
If it's an IF and PF B will have choice of which of the two fouls to accept. Depending on where the personal foul occurs, B may elect to enforce the illegal formation and penalize 5-yds from the previous spot (PS) and replay the down.
If what you saw on the A blocker clocking B, was a USC, then that's a live ball foul treated as a dead ball foul, and B could accept the IF move the ball back 5-yds from previous spot (PS) then tack on an additional 15-yds for the USC, you will still replay the down, since the IF got the replay of the down.
This could be a big double whammy on A, mostly for being stupid.