Sure looks healthy to me, Tom! Please tell us what you have added for fertilizer and at what stage did you add a balanced fertilizer of NPK. I am glad you used potting soil. The pot and soil are too large for this size plant but that is not harming this pepper. In the future, seeds go into tiny pots 1" wide by 2", no larger, roots show then up pot to 3 or 4" wide pot, roots show up pot to a 6" or 1 gallon. All with potting soil. Fertilizer should begin about the 2nd or 3rd set of true leaves. Use half of what the directions tell you. If you used high N (10-8-7) you'll get lots of vegetative growth.
By adding a fertilizer with equal or lower N in relation to the percentages of P and K, you will be 'telling' this plant to think about reproduction.
Small plants in big pots work on roots. Plants fitted to their pot in size switch sooner to top growth. The way to make reproductive growth is by Low N in relation to the P and K: 2-5-4 Growilla. I start out with 5-5-5 after the 3rd set of true leaves. If and when plants show signs of fertilizer deficiency I switch to Growilla to up the reproductive growth.
Making one's own soil where that soil you mixed with the perlite and vermiculite with 20-20-20 is very high fertilizer and to add more I am amazed you don't have fertilizer burn.
Your light is good. I would get a fan blowing 24/7 keep the air moving. That also moves the new O2 and H2O away from the leaves so that CO2 can be uptaken for photosynthesis. Also inhibits fungal disease such as powdery mildew. Plants that are over fertilized, look very very green and are susceptible to fungus, very attractive to sucking insects.
IF THIS truly is over fertilization, which it sure sounds like, I would REPOT this plant into a 6" or 1 gallon pot with cheapo sterilized potting soil with no fertilizer or other gimmicks added (water holding sponges and gels, ugh). To be in charge of the fertilize you have to be the only one who adds fertilizer.
I haven't been able to look at your sites as yet. You've really done a lot of work here and Peppers grow so well and prolifically under lights. I'll go look at this soil and be back.
What color of light spectrum are your bulbs? Blue or Red? Red is for reproduction.
Additional: Tom, I went and tried to find the ingredient label or any details about this compost/coir.
I like that they didn't use peat moss. Very good.
They did not say what 'nutrients' were in that soil but you said the chemistry (not nutrients) was 20-20-20? These numbers mean percentages of the product, so a bit confusing. This block just could not be 60 percent fertilizer!
Do you have availability of plain old sterilized potting soil? Nothing added? I'll look up your fertilizer you are adding weekly??
Another dead end. I have no idea what the percentages are. I am fairly sure you have over fertilized. Your plant is not FRIED, looks healthy. I would repot and not add any fertilizer at all. Change my bulbs to red spectrum. You've got LEDs, yes? You will have to wait a good month to see peppers, I think. Also, you need to think about pollination. You can pollinate the flowers by yourself. I would use a small artist's paint brush. You can also shake the plant now and then.
Please send more information, you've done a great job with what you have sent but I am still assuming an awful lot.