i measure with a refractometer so thats not the problem. the first temp of 154* is the grain/water temp, not strike. I was very happy with my temps, i did lose 6* the first 20 minutes, not sure why, but bringing it back up to 154 was a breeze, burner very low for like 2 minutes, constant stirring.
I have never used maris otter before, so i can't coment, i guess i am looking for a solution that i have never heard of like bad grain, dunno if that is possible, i just don't get it.
i also sparged in a seperate pot after the mash was over. that water looked like I just washed a bunch of potatoes in it...starchy.