It may be worth removing the lemons in the mean time if you have another tank you can set up. Its definitely worth saving the fry, even if its financial. Im sure there are plenty of LFSs that will buy a few discus off you if you get regular spawns, i know that if i had a larger tank id definitely try and get some!
Where did you get your discus from initially? Im heading down plymouth way next week to see family and i was intending to head to plymouth discus to look at their stock, have you had any experience with them being from cornwall (yes im aware plymouth is devon, but its close enough!)?