I'd like to argue that this card needs a cost reduction of 2 to both versions.
Now, I'm fully aware that Nymphs are the Legendary, ultra-rare cards of the game, and that their ownership and use is fully intended to be protected and unusual. However, consider the difference:
A Nymph, currently, is a 8 or 9-quanta card, of an element that's almost certainly a heavy specialization of the deck. Playing one requires only that you have the card.
Nymph's Tears, on the other hand, requires:
a) The sacrifice of 2 cards for one (Tears and quanta source)
b) The sacrifice of a quanta source (this is significant and distinct from a simple card disadvantage, as in point a)
c) A significant, non-trivial devotion of a portion of your deck to water
d) Currently, 2 or 3 quanta less than a Nymph itself
That's four considerable disadvantages - none of them minor - in exchange for a card that requires specific deck construction to take advantage of. Is it the case that a Nymph can be a very powerful card? Absolutely - but most of them are either fragile, damageless, or again, require a very particular deck to deliver well. Given how ultra-rare Nymphs are, it seems reasonable that giving players access to them for competitive play - if they're willing to pay the price - is a good idea. Right now, players, realistically, do NOT have access to Nymphs in competitive play unless they've been ultra-lucky (luck not being the fairest of all masters) or won tournaments (which is a situation of the rich getting richer.)
I'm not suggesting a nerf to Nymphs, and I'm not suggesting they lose their ultra-desired/rare status. I'm simply suggesting that it become SLIGHTLY more feasible (because a card costing 5 or 4 water quanta is still not simple for many decks) that Nymphs be fielded under more circumstances. Could a Rainbow deck double-supernova and throw a Tears? Sure - and they'd have to pray they got the Nymph they wanted and not a useless one. Could the Rainbow deck splash the quanta type they want for the Nymph they wanted? Sure - and now you're talking about a 4 card combo that's praying it won't get hit by a bolt or a dozen other removals. Throw in a Quint to stop it and go-go five card combo! We playing Instosis here?
It will still be far more desirable to simply have a Nymph, but it will stop being basically impossible to see them in play if you haven't either been a champion or fabulously lucky. That, I'd argue, is more fun for everyone.