We had to re-home our cat after he went plotsky because if we didn't he would have been on cat prozac for the rest of his life. It was one of the hardest things I ever did and I still sad about it all these years later.
Your poor kitties must be very confused about why they have been dumped.
Maybe it would be kinder to rehome them if you can't give them the affection they deserve. Maybe in the right home your big kitty could be happy.
Alternatively you could make an effort to fix your relationship with them - maybe put aside 15 minutes each day for lap time and stroking. It's so soothing having a lap full of purring kitty.