The next generation is here! 9 times 5-24 and 9 times 18-24. I plan on always pairing one 5-24 and one 18-24 within a single 40L pot. This will be the F4 generation.
Germination rate was 100%, but one of the 5-24 plants needed a bit of help and isn't out of the woods yet. Interestingly I once again have tricots with this cross, this time it's 2 out of 9 from the 18-24 line. Neither 5-24 nor 18-24 were tricots last year, that was the discontinued 1-24.

So I've discovered something interesting:
The window where I've placed my seedlings wasn't sunny enough over the last week, so some of my seedlings developed edemas. Interesting about this is which seedlings developed edemas.
Only the offspring of last year's 18-24 have issues with edemas, while the offspring of 5-24 are almost completely unfazed.
I'll give them a more sunny location from now on.

There is definitely genetic variance in susceptibility to edema.
I hope your 5-24 are winners in the brix as well, so you can select away from it.

One of the weakened seedlings didn't make it Looks like damping off to me.

Edema when it's bad can be a disaster. Sorry to see it, I've lost plants to that before. If you see edema on the stems, it's frequently fatal. Injuries to the vascular tissue, then the tops aren't getting what they need.

It just so happens that I do have a single 13-24 F4 (third highest brix) left without a designated location (a relative wanted seedlings of the yellow fruited sweet one and I sowed too many seeds). Now I know where to plant it . This way there is a chance for that line to get resurrected from the grave of abandoned breeding lines.

here we go again!

After the weather got better the edema problem mostly disappeared. Some of the affected plants were set back a bit though. 1 died and one is stunted, but the rest recovered nicely and are fine.

I planted 1 each of my 2 major sub lines (5-24 and 18-24) in each container. One of the containers features the last minute wildcard contender from the 13-24 line, which took the place of the plant that died from edema.

I took care to use exactly the same potting mix in each container:

40L of cheap peat based potting mix (ph: 6.0 N: 150 mg/l P: 500 mg/l K: 1500 mg/l Mg: 220 mg/l S: 340 mg/l) + 5 double handfuls of vermiculite + 3 double handfuls of perlite + 1 double handful of fertilizer.