[Elecraft] K2 PSK Question

[NR5A]

I mainly run PSK 31 with my K2. On 80, 40, 30, and 20m I get my normal 5
watts output PSK31 and cw. I have noticed in certain areas on PSK my output
varies. Tonite I tried 15m for the first time, here is the problem. I tuned
up 21060 and got my normal 5 watts output, now moving to 21070 I hit tune,
SWR was the same, power output was still 5 watts. I called cq on PSK and
can't get much more than 1/2 watt output. Turning up the power contol does
not incease output. Anyone have a clue on whats going on?

Jerry - NR5A