I'm having difficulty converting lumens into the units I am more familar with - foot candles or lux ( metric system) .
But first Calanthe - that is a terrestrial, grows on the ground in rain forest, so gets low light - 1/10th the light of a cattleya at a guess, maybe even less - I once found Calanthe triplicata growing in 33 Lux, ( about 3 ft. candles) when orchids in the canopy of the forest got light measured in K lux ( thousands of lux ).. You are making life difficult for yourself if you try to grow too wide a range in your conditions. Most cattelyas do really need it bright - I try to achieve 20000 lux ( 20K lux) on mine - which I do with 400 watt sun lamps plus full daylight . And if you go too near the lamps you may get some kind of burn.
Leaf colour - yellow just means a dieing leaf as a rule - normal on even evergreens, when the leaf gets to the end of its life, usually because the roots directly beneath that leaf have got to the end of theirs, but 4 years life is about max. Too much light tend to lead to red colour , not yellow - think of it as sunburn.
You have started on a long learning curve, but one worth the effort, believe me ; I have been growing for 51 years now, and I'm beginning to realise a few of the things I have still to learn...