Ok, slight over reaction

I have always had really quick growing, strong nails. Never needed any treatments and weren't affected by varnish or the way I filed etc. People used to comment on how lovely they were
Well, that will teach me to be smug about them as they are a right mess now! 
Always split at the ends, a couple really badly. They look really weak and out of condition.
I have used Sally Hansen Miracle Cure - it did work but do you keep on using it?
Do I need to take supplements and if so and what sort - I looked in Boots and couldn't find anything specific?
I am this close to painting nail glue on the ends to seal them and give them a chance to grow.
I have a Leighton Denny file - they are still growing fast so need cutting once a week, should I use clippers then file or just the file? Maybe its the clippers that are making them split?
Any suggestions gratefully received 