I have two little ones that I was having exactly the same problems with. I was assist feeding fuzzies once a week. They weren't gaining any weight, and in fact the spider female was losing weight. I finally decided they were going to gain weight. I went to an every 3 days feeding schedule, and assist fed 2 fuzzies (chasing the second one). After a couple feedings, I started chasing with a hopper. Then to just a hopper. Weight gain started right away, and their strength increased dramatically. About 3 weeks in, the normal female started eating on her own, ravenously. I gradually, but quickly bumped her up to adult mice, and cut her back to once every 5 days. The spider still wasn't eating on her own, so I filled her tub with balled up newspaper. About a week after that, she started eating on her own, ravenously! She, too, went to adult mice right away, and cut back to every 5 days.
I ALWAYS offered a live fuzzy/hopper first, leaving it in for about 20 to 30 minutes before resorting to assist feeding.
So, my recomendation is to continue assist feeding (offering first) on a schedule that will build that little snake up. I really think the added weight/strength had a LOT to do with them starting on their own. Also fill the tub with balled up paper for added security. This has worked for me several times now with reluctant feeders.
Good luck!
Steve