In Saturday's sprint race, Alonso was given a 10-second penalty for a glancing collision with Ferrari's Carlos Sainz towards the end of the race, which resulted in Alonso retiring with a puncture.
The next day Stroll received a similar penalty for crashing into the back of RB's Daniel Ricciardo under safety car conditions, which caused terminal damage for the Australian and also damaged Oscar Piastri's McLaren.
Having judged the steward's swift penalty decision for Stroll as "very harsh", Krack went on to say the "stewards have been tough to Fernando and Lance recently".
That includes Alonso's penalty for 'potentially dangerous driving' in Australia, where his extremely early braking for a corner caught out the chasing Mercedes of George Russell, who crashed off in his dirty air.
"We had it in the sprint race, we had it in Melbourne, we had with Lance [here]," Krack said.
"Last time it was the car in front that got the penalty [Alonso] in Melbourne, even without touching. This time, it was the car behind."
Krack pointed to Stroll's first-lap contact in Bahrain, in which he was spun around by Haas' Nico Hulkenberg, as an example of others escaping punishment.
Source: Autosport