If they are 4 months old, speak to Hope – they are very helpful and will happily give advice. Ultimately, they may want them back to fettle (aka rebuild) them.
I used to get this and ultimately used to service them once a year – i.e. strip the lever and calipers, clean thoroughly and then rebuild with new seals. It’s an evening’s work, and needs a bit of patience to do, but there’s no magic needed.
Oh, and Castrol Red Rubber Grease on the pistons too 🙂 (although recently, I’ve heard that you shouldn’t use anything on them at all as it just attracts the grit into the seals – this makes a lot of sense, actually)