It might be that there's been too much rain - rhubarb is usually pretty tough (not in texture
) If I were you I'd spread some good manure around (not on the crowns, just on the soil around them) and then leave well alone for the summer - just making sure that you hand pull any weeds that pop up.
We've had such a wet winter and while rhubarb doesn't mind the cold it's not keen on wet cold, so it may be that your rhubarb needs to enjoy this sunshine - I think I'd not crop it any more for the moment and let it put on some growth - I'm sure it'll be fine.