Great advice given by Itzjbean...
Right now it is extremely important that YOU do not reduce the number of formula feedings your bird is getting nor the amount of formula in each feeding, that must only be decided by your bird!!! What you are accidentally doing by taking away a formula feeding is called "Force-Weaning", and it's a very detrimental thing to do to a baby bird, and will cause life-long neurological, psychological, and behavioral issues if you do it...Your bird is the only one who can decide to "take away" a formula feeding, or to reduce the amount of formula per feeding because he is eating enough solid food to do so...
At only 8 weeks old, your bird is pretty-much right on track at 3 formula feedings a day, so I highly suggest that you add the formula feeding that you took away back, and basically "start over" the "Abundance Weaning" process.
As wisely suggested by Itzjbean, the best way to start your bird weaning onto solid food is by putting a millet-spray into the bird's weaning-cage/brooder. So I would go right back to offering your bird a formula hand-feeding first thing in the morning, then put a millet-spray inside his weaning-cage/brooder, and then offer a second formula feeding as soon as you see that his crop is almost empty, probably some time in the mid afternoon, and then another formula feeding before bed, as soon as you see his crop almost empty again...And watch to see that he's starting to nibble at the millet-spray, usually they start very early, as early as 5 weeks-old on the millet-sprays....As soon as you see that the millet spray is gone, give him another one, and it should disappear more quickly than the first one did, and so on.
As soon as you know that your bird is eating the millet-sprays without any issues, then you need to put a bowl of a quality, Cockatiel seed-mix into his weaning-cage, NOT just sunflower seeds...The last thing you want to do is to wean your bird directly onto sunflower seeds, because then he will just reject all other seeds/pellets and beg for nothing but sunflower seeds, and he'll end-up with very early Fatty Liver Disease, Diabetes, etc. So stop the sunflower seeds completely right now, and go and choose a high-quality, low-fat seed-mix (cockatiel/conure size), that doesn't contain any sunflower seeds, no peanuts or other nuts, and no corn. These are the things you do not want him to start eating in his daily diet...There are lots of choices of "sunflower-seed Free" seed mixes, that's what you want, and you can find many at any Petco or Petsmart. If it has sunflower seeds, peanuts, or corn in it, do not buy it!!!
So add a bowl of the high-quality, low-fat seed-mix into his weaning cage, and watch to see that he's eating it. You should be weighing him every single day, first thing in the morning before you feed him his formula, to make sure that he's gaining weight or staying the same, and not losing...The hand-feeding formula is specially made for developing, rapidly-growing baby birds, and that's why you absolutely cannot just "take away" a feeding of it, that has to be his choice based on the fact that he's full from eating the seed-mix...And as time goes on, the more healthy, low-fat seed-mix and fresh veggies he eats, which you can offer him at any time along with the seed-mix, the less formula he will eat in each hand-feeding...And then eventually he'll totally refuse a hand-feeding, and replace it with the seed-mix and fresh veggies. And this will continue until he's only begging for a nightly hand-feeding of formula, called a "comfort feeding", which is more psychological than the fact that he's hungry...
The millet-spray will get him started eating seeds. As soon as you notice him eating them, then start the healthy, low-fat, sunflower, peanut, and corn FREE seed-mix...But do not attempt to take away any formula feedings or the amount of formula in a feeding on your own, or your bird will end-up with serious issues for the rest of his life...
Also, as Itzjbean also mentioned, you absolutely have to make sure you have a candy/cooking thermometer in the hand-feeding formula the entire time you are feeding it to him, and it must be between 104 degrees F at the lowest, and 110 degrees F at the highest...If it is one degree lower than 104 he can develop a fungal/yeast infection in his crop, develop slow-crop or complete crop-stasis, and also they tend to not want to eat the formula if it is cooler than 104 degrees F....If the formula is even one degree hotter than 110 degrees F it can severely burn his crop and cause a horrible infection, which is only remedied by a Vet doing surgery and basically cutting a hole in his crop to remove the infection/burned tissue and then letting it close-up on it's own...So if you're not already using a cooking/candy thermometer in the formula the entire time you're feeding it to him, you must go to Walmart or somewhere else and buy one; a digital cooking/candy thermometer with a metal probe you insert in the formula costs $10-$15 at Walmart...And the older he gets, usually the thicker they like their formula...