Rumble & Tilly are battling me over their food!!!!

Rumble & Tilly a month or so ago went on to my Allen & Page food 100% but they are protesting.  For months they have been on 75% Allen & Page & 25% Burgess Excel & had been eating both albeit the Burgess went first.  But now since going over completely they are both on hunger strike.  A very reduced amount of Allen & Page food is being eaten & a lot of it is being left resulting in a significant weight loss for both of them. I have been advised that anymore than 20% of their bodyweight is really the limit of what they can loose & Rumble probably has another week & he’ll be at his limit – I will then have to cave in & give him the food he wants!
I know it’s said that they won’t starve themselves to death but I am starting to wonder.  Rumble is a very stubborn rabbit when he wants to be & I am sure Tilly is just following suit.  On a positive note, yesterday they have eaten the second lot of  Allen & Page breakfast I gave them.  Rumble in disgust threw his first lot of breakfast at me & this morning a third of their food was left.  The Allen & Page is a far better food for them if only they’d understand.  Everybody else has done really well on it.
This tough love is very hard!!