I recently built my first soil and ended up not adding enough lime and my ph was low and my plants looked just the same as yours with new growth being pale
I cant say for certain ph is the absolute issue since you cant check it and im sure there are other things that could cause the very mild yellowing
I sprayed about 3x over a couple weeks with some calcium, magnesium and micro nutes until the lime kicked in and it did the trick... bringing the ph up to range
yours is mild enough thou where you might consider doing nothing and re-asses in a week