Insurance firms have been increasing their interest in crypto investments since December.
The digital asset manager added large numbers of altcoins to its holdings including horizen and livepeer.
GBTC’s premium flipped negative one day earlier.
Bitcoin and ether continue to rise, but that could create problems for overheated derivatives markets.
Investor excitement ahead of the CME's planned ether futures contract is one reason for the price push.
The firm's bitcoin assets under management rose by more than $3 billion in a week.
Grayscale periodically closes off its crypto trusts to so-called "private placement" rounds.
Grayscale's bitcoin and ether trusts now make up almost the entire $13 billion in AUM value.
Existing shareholders will receive eight additional ETHE shares for each one held, with each new share being a ninth the value and price of the current ones.