I suspect your right and that pH is the biggest influence, only cost you $30-40 for a not too bad pH meter, if its making that big a difference you will pay it off in malt savings over half a dozen brews, worth thinking about and get some decent Acid to.
Just your calculated yield at 70% of 1.037, and your reported 1.050
37 points at 70%, 37/70*100=52.8 at 100%. 50/52.8*100=94.6%.
Not really accurate just a quick and dirty to see about where you were, assumes you used the same amount of grain and made the same amount of wort... Figured you would know that if the volume was a lot less the SG would be a lot higher and all that.
Just had a glance at your Brewers Friend, couple of things, I don’t use BF, mostly just do calcs on a piece of paper
PPG and Lovibond aren’t really much use here, everything sold here is or should be quoted in Metric units.
Don’t add Chalk unless you want to Raise the pH (rarely)
I doubt you are getting Anhydrous CaCl2 - worth checking the form its supplied to you in but it’s probably the Di-Hydrate.
Change the citric for a better acid, goes back to the chalk, adding chalk then neutralise it with acid doesn’t make sense.
As I said I don’t use BF, but that "Hop Utilisation" looks very odd, home brewers usually get 20-30%, good commercial kettles maybe over 35% but not much over. Its saying 98%, I'm not sure how that’s calculated but would want to know before I trusted it.
Say you had 25L at the end of boil. Looking at the first hop addition 40g of Fuggle at 4.5%, giving 24IBU
Starting Alpha is 40g*4.5% = 1.8g of Alpha Acid
24IBU is 24mg/L or in 25L, 24/1000*25 = 0.6g
0.6/1.8 = 33% Maybe a bit ambitious but makes more sense than saying 98%
Mark