I dont know specifically about french lops either.
All I can say is with my doe who had her ten babies, because there were so many I counted them out morning and evening to check them all.
I'm not saying my way is correct i just read through the net and decided that this is what i would do.
I'll just put it down in the hope of being useful
My doe had a nest box, that she made her nest in, in the dark part of her hutch with the closed of door. In the morning, I'd put her out into her run, without the babies of course, they stayed in the nest.
Once she was out I then rubbed my hands in her litter and checked each one of her babies, to check their bellies had a round appearance and were not sunken or wrinkly.
If I had to get to work I'd put mumbun back after I'd checked through and replace the nest box, if not, then I'd let Tam have a couple of hours in her run munching grass, even Mumbuns have to have some downtime!
I did the same again in the evening, Tamlin (mumbun) into her run and checked every baby.
I did this religiously because I'd heard that if one baby died, of course it would go cold, it then put the other babies at risk of pnuemonia I believe cos they would then get chilled from lying next to the dead one.
After 1 week a couple of the babies were looking smaller/less nourished than the others. Because they had come this far I felt I couldnt just let nature take its course, on my vets advice I supplemented mumbun's milk with some kitten milk with probiotic added. I fed them from a syringe, really allowing them to lick it from the tip rather than putting it into their mouths and risk drowning them.
I did this pretty much same as before, they still all stayed with her but I'd put her out in the run and bring the whole nest box indoors.
I dont know if any of that helps or sheds any light onto the situation you've had. The only thing I can think of is that you remove your mumbun (if you decide to try again) from her hutch entirely and into a run while you check the babies thoroughly so she wont be worried by your presence near the babies.
With regard to diet, does your lady bun eat a pelleted food? If yes, great, if not, you may wish to change her onto one, a pelleted food prevents selective feeding and makes sure bunny gets all the vitamins and minerals she needs.
I was also advised by my vet that my mumbun, who was previously on Excel pellets, should be on Excel Junior and Dwarf pellets which is for pregnant/lactating does or smaller breeds. I cant recall exactly but I'm pretty sure Tamlin had unlimited pellets and hay etc during the first month or so of her feeding them.
Do you have a good relationship with your doe? Sorry, what I mean is, is she usually grumpy or does she not mind you around your hutch etc usually?
While Tam was pregnant I used to just sit with her a long while giving her noserubs and laying my hand on her belly while she lay, i could feel the little ones move inside. I know not all buns are the same and some are mardy mares, but Tam was very shy, still is, but I think she kinda learnt that I wouldnt do her any harm and I think I probably always put her in her run too when I cleaned her out, so I hope she never felt I was 'invading' her space.
Tamlin's babies were born 2nd October. The weather was still quite mild then. I guess there's no way of knwoing if weather played a part, many does do mother litters in the cold to no ill effect but a spring mating is probably the best time to remove that variable.
Sorry, non of this is of course breed specific and I may have just said stuuf you already knew or have done but in the hope of beign helpful I thought I'd put it down.
It still may be I guess that your doe just isnt a natural mother :? as Sky-O says to line up a foster mum would prob be a good idea if you were to try again.
I still, in my opinion, believe neutering your two and letting them live happy ever after, and maybe fostering for a rescue and taking care of a pregnant rescue doe and raising a litter that way would be a better use of your love of bunnies
but hey.
I hope your research gives you the answers you need x