Hi there, if he settles does he stay asleep for long or does he re-wake soon after? To be honest in the first 6 mths up to the 6 mth growth spurt I always check the hunger situation really because they just really do go through so many GS in that time. I think I would offer it for the next little while, few days to see if it just settles itself. If it becomes a habit then it is likely a routine issue.
I agree I would bump up that first A time with a 1 hour nap, it does sound a bit UT. But be careful sometimes with these guys (like my DS) when you bump up one A time the next A time can reduce slightly while they get caught up so to speak. When I pushed out Finn's morning his middle A shrank a bit until he was used to the longer A time and had a decent nap. Could you try 2.75 first, 3 hours seems a big jump at 6 mths really. The second nap in your routine above also strikes me as a bit UT.