It's not strange at all. Look what's happening:
run 1 > T1 = 05s, T2 = 5.2s
run 2 > T1 = 10s, T2 = 10.4s
run 3 > T1 = 15s, T2 = 15.6s
See? The distance between them is getting larger, and this is because of how you set it up. You want 0.2s after Timer 1 ends, not 5.2s after Timer 1 begins.
What you need to do is set Timer 1 with 5s and Timer 2 with 0.2s. Then, when Timer 1 times out, start Timer 2.