When a security is in a downtrend the price will touch the last support(dark green line) more often. In this example of USDCAD , it's on a 15 minutes chart, after the price reached a bottom, the reversal only back to the middle (light green line). It's very common that the weakest support(light green line)became the strongest resistance in downtrend.
In a downtrend all lines will move downward in next session. In this pic, you can see that the second last support line of current session is almost equal to the last support line of previous session.
When price break through the last support line(dark green line) of previous session, the next stop is the last support of current session.