Swing speed stalls after 7i with irons (6i, 5i, 4i)

My general swing speed for clubs is about 80-92mph from my 58 to my 7i, however my next 3 irons all stall out and fall between 90-91. All irons are .5" long. My 3 wood is about 103mph at stock length (always off turf) and my driver is about 108mph cut down 1.25".

There's generally about 10-12 yards carry between each my clubs (PW - 7), but then only about 5y between each of the clubs beyond that. And then a massive 40y carry between my 4i & 3w (off turf). I've been intending to get a new club to fill the slot between those clubs but I'd really like to dial in my long irons before I settle on a 5w or a 2i/3i driving iron (I hook the shit out of hybrids).

Are there any general tips to hit the long irons faster?