I had to replace the three LED's on the power side on one board. A silly mistake, I fitted J1 transistor the wrong way and when I powered up all LED's came on but one channel went out after a minute, I had two LED's left over and had to buy another from Mouser. I checked the FV of the new one and it was 1.650v and I think I remember the kit ones were ~1.850v - I now can't reach 34v output (33.8v max) from that channel with the pot at the end of its travel, and I think the new LED is slightly brighter than the already installed two.
My question is would that 0.2v lower FV on one LED be enough to prevent me achieving the 34v output - the other channel is perfect and both have 39.4v input from the Raw supply.